NEW YORK • The recovery last month of Willem de Kooning's Woman-Ochre 32 years after it was stolen raised as many questions as it answered.

Investigators are trying to determine if the heist was engineered by a retired New York City schoolteacher - something of a renaissance man - who donned women's clothing and took his son along as his accomplice, and then hung the masterwork in the bedroom of his own rural New Mexico home, where it remained.

In other words, they are examining whether he stole a painting now valued at in excess of US$100 million (S$134.8 million) simply so he could enjoy it.

The teacher, Jerome Alter, and his wife, Rita, both died at 81 - he in 2012 and she this summer.

"My driving instinct is to say: 'This couldn't be my aunt and uncle who had it since the beginning,'" said Mr Ron Roseman, Rita Alter's nephew. "But, well gosh, it's like I said, I'm as clueless as everybody else. It's hard to believe that they were that - I don't know what the word for it is."

Mr Roseman, who lives in Houston and is the executor of his aunt's estate, was mystified as to how the painting had ended up in his aunt and uncle's quirky one-storey pink ranch-style house in Cliff, a hamlet of barely 300 people more than 359km from the museum in Tucson.

It was the day after Thanksgiving in 1985. An older woman and a younger man walked into the museum about 9am. A security guard had just unlocked the glass doors to admit an arriving employee, whom the pair followed inside. The sky was overcast and it was 13 deg C; both of the visitors wore heavy winter coats.

A few minutes later, the two left in such haste that they attracted the attention of staff members. One museum employee hurried up the steps to the second-floor gallery, where the man had spent less than 10 minutes while his companion asked a security guard about another piece of art.

The 100cm by 75cm de Kooning painting - completed in 1955 and depicting a defiantly naked figure facing the viewer, arms akimbo - was gone.

Investigators believe the man cut it from its frame and rolled up the canvas and stuffed it under his heavy blue coat while the woman distracted the guard, who could not see the gallery from the landing where they had talked.

The two drove away in a rust- coloured two-door car. At the time, Woman-Ochre was valued at US$400,000.

It was a highly unusual crime.

Despite the depiction of art heists in movies and television, a vast majority involve works taken from storage areas by employees or people in a position of trust. With few leads beyond a description of the thieves, the crime became an enduring mystery.

"We're looking at everything," said Mr Brian Seastone, the University of Arizona police chief, when asked about whether investigators were looking into the possibility that Jerome Alter and his son, Joseph, were involved in the theft.

He would not say what other avenues were being pursued.

The university police department is assisting the Federal Bureau of Investigation (FBI) with the case.

Ms Jill McCabe, a spokesman for the FBI in Phoenix, would not comment other than to say that the bureau has "an active and ongoing investigation into the theft".

The sketch of the female suspect - described at the time of the theft as being between 55 and 60 years old - bears a resemblance to Jerome Alter, who was known as Jerry and was then 54.

And the sketch of the young man - described at the time as between 25 and 30 years old - bears a resemblance to his son, Joseph M. Alter, who was then 23.

At around that time, the Alters had a red two-door Nissan sports car, according to a family member, a family friend and owner of a gas station less than 2.4km from the Alter home.

Joseph Alter, now 55, who has lived in Silver City, about 50km from Cliff, could not be reached for comment.

Several people who knew his parents, and Mr Roseman, said Joseph has had severe psychological problems since the mid-1980s and has been in and out of mental institutions. Mr Roseman said he was currently hospitalised.

Jerome Alter's sister Carole Sklar, 81, an artist who lives in New Jersey, scoffed at the notion that either her erudite, cultured brother or his sweet, gentle wife - let alone their troubled son - had been involved in the theft.

She called it "absurd" and said the notion that her brother would dress in women's clothing was laughable. "That Jerry and Rita would risk something as wild and crazy as grand larceny - risk the possibility of winding up in prison, for God's sake - they wouldn't do that," she said.

The Alters built their three-bedroom house, set on 8ha of rugged scrub brush on a mesa overlooking a mountain valley, after they moved to New Mexico in the late 1970s.

In addition to teaching music in a New York City school in Washington Heights, Manhattan, Jerome Alter worked as a professional clarinettist before retiring to Cliff. Rita Alter worked for a number of years as a speech pathologist in the public schools in Silver City.

The couple, who people in Cliff said largely kept to themselves, were avid travellers, having visited more than 140 countries on all seven continents, according to a book of fictionalised short stories based on their trips that Jerome Alter self-published in 2011.

Mr David Van Auker, an antiques and furniture dealer whom Mr Roseman hired to appraise the contents of the Alters' home, discovered the painting. He and his two business partners went to the house on Aug 2 to photograph and catalogue the furniture and other items for sale after Rita Alter's death.

He found Woman-Ochre hanging between a corner of the bedroom and the door, he said, situated so that it was obscured when the door was open, but visible from the bed when the door was closed.

While he did not recognise it as a masterwork, he liked it and ended up buying the contents of the house for roughly US$2,000, he said. He took the painting back to their store in Silver City and, that day, several patrons who saw it on the floor said they thought it was a de Kooning.

Some determined Google searching turned up photographs of the stolen artwork and an Arizona Republic story from 2015 about the 30th anniversary of the theft.

Mr Van Auker called the museum that evening and, a day later, a Friday, a team of excited staffers were in Silver City examining the painting. They took it back to Tucson the following Monday.

"This is a moment the institution has been talking about and thinking about since the painting was stolen," said Ms Meg Hagyard, the institution's interim director.

NYTIMES