NEW YORK (NYTIMES) - The memos were concise and direct.

An executive at Johnson & Johnson said the main ingredient in its best-selling baby powder could potentially be contaminated by asbestos, the dangerous mineral that can cause cancer. He recommended to senior staff in 1971 that the company "upgrade" its quality control of talc.

Two years later, another executive raised a red flag, saying the company should no longer assume that its talc mines were asbestos-free. The powder, he said, sometimes contained materials that "might be classified as asbestos fibre".

The carcinogen, which often appears underground near talc, has been a concern inside the company for decades. In hundreds of pages of memos, executives worried about a potential government ban of talc, the safety of the product and a public backlash over Johnson's Baby Powder, a brand built on a reputation for trustworthiness and health.

Executives proposed new testing procedures or replacing talc outright, while trying to discredit research suggesting that the powder could be contaminated with asbestos, according to corporate documents unearthed by litigation, government records obtained by The New York Times through the Freedom of Information Act, and interviews with scientists and lawyers.

In one instance, Johnson & Johnson demanded the government block unfavourable findings from being made public. An executive ultimately won assurances from an official at the Food and Drug Administration that the findings would be issued only "over my dead body", a memo summarising the meeting said.

Those efforts are now forming the crux of a new legal front in a long-running battle over Johnson's Baby Powder, potentially leaving the company exposed in nearly 12,000 lawsuits across the country claiming that the product can cause cancer.

This summer, 22 women with ovarian cancer successfully sued the company, arguing that Johnson & Johnson knew about the connection between talc and asbestos. A jury in St Louis awarded them US$4.69 billion, one of the largest personal injury verdicts ever.

The company lost two other cases this year, in California and New Jersey, brought by people with mesothelioma, a cancer of the lining of internal organs that is associated with asbestos.

The prospect of asbestos "puts the defence in a much more difficult position", said Nathan Schachtman, a lawyer who has defended asbestos companies. "You get a much higher degree of indignation from juries."

Shares of Johnson & Johnson dropped 10 per cent on Friday on an article by Reuters about the asbestos concerns related to Johnson's Baby Powder.

Johnson & Johnson is appealing against the three asbestos-related cases. The company has won three cases related to mesothelioma, while four others were declared mistrials.

The company defends the safety of its baby powder, saying it has never contained asbestos and the claims are based on "junk science". Johnson & Johnson says the lawyers in the cases have "cherry-picked" the memos, and that they instead show the company's focus on safety.

"Johnson & Johnson's talc has been tested by scientists at multiple entities since the early 1970s up to the present," said Peter Bicks, a partner at Orrick, one of the law firms representing the company in the lawsuits. "None of these routine tests over the past 50 years detected the presence of asbestos."

For more than a century, Johnson & Johnson has promoted its baby powder as pure and gentle enough for babies' bottoms, a product that mothers can trust, made by a company that puts customers first.

The company's image has long been bound up in the product and its iconic white bottle, even though baby powder counts for only a sliver of overall sales. Its fragrance is said to be among the most recognisable in the world. Employees have called it a "sacred cow" in e-mails, according to court documents.

Krystal Kim, a 53-year-old mother of two from Philadelphia, was 10 when her mother suggested she use Johnson's Baby Powder to stay "fresh" and "clean smelling".

She continued using it for decades, on her face, between her legs and on her sheets.

Many women use baby powder as a feminine hygiene product, applying it to their bodies and breathing in airborne powder.

Five years ago, Kim learnt she had invasive ovarian cancer and was treated with chemotherapy. Parts of her colon and intestines were removed. Kim, one of the plaintiffs in the Missouri case, wants Johnson's Baby Powder taken off the shelves and, if not, warnings put on it.

Before the Missouri verdict, Johnson & Johnson had been able to knock back most of the legal challenges that connected talcum powder alone to cancer, by claiming, in part, that the scientific research was flawed and offering studies to the contrary.

Of the six cases that Johnson & Johnson has lost on that issue by itself, three decisions were overturned on appeal, one is still under appeal, and one plaintiff won her case but was awarded no damages. One verdict, for US$110 million, has been upheld by a judge; the company is filing an appeal.

But asbestos, unlike talc, is an indisputable carcinogen. Even trace amounts are considered dangerous. Its dagger-like fibres penetrate deep into tissue and can lead decades later to cancer of the lungs, voice box and ovaries, and to mesothelioma.

Several lab tests, some conducted in the past few years by plaintiffs' lawyers, have found evidence of asbestos in talc. The link between asbestos and ovarian cancer was first reported in 1958, and in 2011, the International Agency for Research on Cancer said it was a cause.

"There's no ambiguity," said Mark Lanier, the lawyer who represented the women in the Missouri case. Lanier has won large industry payouts for workers who were exposed to asbestos on the job.

"It's a no-brainer that asbestos causes ovarian cancer," he added. "That's not an argument anyone will win."

Legal Roadblocks

Darlene Coker developed mesothelioma in 1997. But Coker, then 52 and living in Beaumont, Texas, had never worked in shipyards, construction or mining, like many mesothelioma sufferers. She was a lifelong user of Johnson's Baby Powder.

When she sued Johnson & Johnson, she didn't get far. As part of the discovery process, her lawyers tried to get information about asbestos from the company. Its response: There wasn't anything relevant.

When they asked for names of labs that had tested Johnson's talc for asbestos and records of the test results, Johnson & Johnson told them that the questions were "vague". Requests for documents were declined for being "over broad and unintelligible", according to legal filings. The company called it a "fishing expedition".

Coker's lawyers withdrew the case. She died in 2009 from mesothelioma.

Lanier, the lawyer in the Missouri case, said he planned to revisit Coker's lawsuit now that the documents obtained in recent cases showed that the company did have information to share.

The recent spate of asbestos-related cases, which has unearthed the troves of internal Johnson & Johnson's documents, is prompting a broad legal rethink by plaintiffs' lawyers.

After the Missouri trial, Michael J. Miller, a lawyer in Virginia involved in the talc litigation, said more plaintiffs lawyers were considering whether their clients' ovarian cancer was linked to asbestos.

"We knew for years that there was something about the talc that caused ovarian cancer, and there had been rumors about asbestos, but we were really being stonewalled by Johnson & Johnson about the documents we needed," he said. "The trial in St Louis was very instructive, very informative, and it's got us all enthused."

Miller's firm represents 900 plaintiffs who have blamed their ovarian cancer on long-term use of Johnson's Baby Powder. He expects his first trial in early 2020.

"We didn't even need to know there was asbestos in there to win these cases, but now that we know, it makes it even easier," he said. "We're all eager to get to trial."