SAN FRANCISCO • For more than a year, regulators in various cities have questioned whether Uber, the ride-hailing service, vets its drivers for criminal backgrounds as carefully as traditional taxi companies. Now the district attorneys of San Francisco and Los Angeles have offered perhaps the most concrete evidence to date that people convicted of murder, sex offences and various property crimes have driven for Uber, despite assurances from the company that it employs "industry-leading" screening.

The district attorneys said on Wednesday that background checks used by Uber failed to uncover the criminal records of 25 drivers in the two cities.

The charges were made in a 62-page amended complaint to a civil suit, originally filed in December, that claims Uber has continually misled consumers about the methods it uses to screen drivers.

"We are learning increasingly that a lot of the information that Uber has been presenting the consumer has been false and misleading," said Mr George Gascon, the district attorney in Uber's hometown, San Francisco.

As Uber has aggressively pushed its service into cities around the world, often not waiting for permission from local regulators, it has faced hostility from local taxi drivers who fear it is undercutting their business, as well as increasing scepticism regarding the trustworthiness of some of its drivers.

Some of the most pointed questioning has come from Mr Gascon, who argues that Uber's background checks are not as thorough as another service, called Live Scan, that is typically used by taxi companies.

He said at a news conference on Wednesday that about 30,000 registered sex offenders in California did not appear in a public registry Uber uses in its background checks. The checks also go back only seven years.

"So, for example, if someone was convicted of kidnapping eight years ago, and they were just paroled last week - they just got out of prison - the Uber background check process will not identify the person as a convicted kidnapper," Mr Gascon said.

He said this was "troubling and misleading to Uber customers and to the public at large" because Uber says its process goes back as far as the law allows. Mr Gascon was careful to couch this as a case of consumer deception.

Uber is not by law required to use the Live Scan system favoured by district attorneys.

The question is whether the consumer is getting all the right information, he said.

The suit, which Mr Gascon said "is only really scratching the surface", does not name the criminals but includes some details about their crimes.

• One driver was convicted of second-degree murder in Los Angeles in 1982, and spent 26 years in prison before being paroled in 2008. He applied to be an Uber driver under a different name from those in his court records.

• Another driver was convicted of felony sexual exploitation of children in Wyoming in 2005, and another of "felony kidnapping for ransom with a firearm" in 1994.

•Other drivers were convicted of charges like robbery, assault with a firearm, identity theft and driving under the influence. Several were convicted of more minor charges, like welfare fraud.

An Uber representative said in a statement that the company's background check method was no worse than Live Scan.

Uber, which recently celebrated its fifth anniversary, is already valued at about US$50 billion (S$70 billion) by investors. The company has raised a multibillion-dollar war chest to finance a global expansion and to move into areas like food delivery.

NEW YORK TIMES