A young Frenchwoman of North African origin, she opted to wear an Islamic veil, though she said the pious choice of attire cost her a job as a cashier. She has accused the U.S. of killing innocent Muslims, and was photographed wielding a crossbow.

Never convicted of a crime herself, Hayat Boumeddiene, 26, was being sought Saturday by French police, who think she may have vital information about an Islamic extremist cell that her common law husband, shot dead by police, may have belonged to.

French authorities, though, may be too late in their hunt for the missing widow. Turkish authorities told The Associated Press that she may be in Syria, after passing through Istanbul last week and vanishing near the Turkish-Syrian border.

"On January 2, a woman corresponding to her profile and presenting a piece of identity took a flight from Madrid to Istanbul," a source familiar with the situation told Reuters.

The source said she was accompanied by a man and had a return ticket for January 9, but never took the flight.

A senior Turkish security official said Paris and Ankara were now co-operating in trying to trace her, but said she arrived in Istanbul without any warning from France.

"After they informed us about her ... we identified her mobile phone signal on January 8," the source said. "We think she is in Syria at the moment but we do not have any evidence about that ... She is most probably not in Turkey," the source said, adding the last signal from her phone was detected on Thursday.

In a 2010 interview with French counterterrorism police, a summary of which was obtained by the Associated Press, Boumeddiene characterized herself as an observant Muslim, and her late common law husband Amedy Coulibaly, 32, who worked at the time for Coca-Cola, as somewhat of a party animal.

Coulibaly "is not really very religious," Boumeddiene told police, according to the official judicial documents. "He likes to have a good time (and) all that."

French media described her as one of seven children whose mother died when she was young and and whose delivery-man father struggled to keep working while looking after the family.

'We must interrogate her'

The pair wed in July 2009 in an Islamic religious ceremony not recognized by French law. The judicial records say she was known to French internal security services as being very close to Islamic radicals, and an official circular distributed Friday by French police said she should be considered dangerous and potentially armed.

At dusk Friday, Boumeddiene's husband was killed when police stormed the kosher market in eastern Paris where he had taken hostages. French prosecutors said Coulibaly killed four people before police put an end to the ordeal.

Hayat Boumeddiene? social media photo

French media have released photos purporting to be of a fully-veiled Boumeddiene, posing with a cross-bow, in what they said was a 2010 training session in the mountainous Cantal region.

At virtually the same hour near the Charles de Gaulle airport outside the French capital, two brothers suspected of killing 12 people at the Charlie Hebdo newspaper on Wednesday died in a shootout with police.

It's Boumeddiene who may have key information about how the attackers were linked, officials said. She and the female companion of one of the Kouachi brothers talked to each other by telephone about 500 times, Francois Molins, the Paris public prosecutor, said Friday.

"We can call this complicity by furnishing of means," Christophe Crepin, spokesman for the UNSA police union, told the AP in an interview. "We must interrogate her so she explains exactly if she did this under influence, if she did it by ideology, if she did it to aid and abet."

For Paris authorities, Coulibaly's widow "is considered an important witness to whom we must ask questions," added Crepin. "Since 2010, she has had a relationship with an individual whose ideology has been expressed in violence, and by the execution of poor people who were just doing their shopping in a supermarket."

Official judicial records show Boumeddiene was asked once by French counterterrorism police about her reaction to attacks committed by al-Qaeda.

"I don't have any opinion," she answered, according to the documents, but added immediately that innocent people were being killed by the Americans and needed to be defended.

The same year she wed, she told police, she began wearing a full-length Islamic veil —a decision, she told her interrogators that led to losing her job.

On Saturday night, a Turkish intelligence official told AP that authorities believe Boumeddiene arrived in Turkey days before the attacks that shook France, and may have crossed the border into Syria.

'She then disappeared'

The official, speaking on condition of anonymity, said a woman by the name of Boumeddiene and who resembled a widely circulated photo of her flew to Istanbul on Jan. 2. Turkish authorities believe she travelled two days later to the Turkish city of Sanliurfa, and "she then disappeared," the intelligence official said.

France Newspaper Attack

Two police officers stand guard a day after the terrorist attack on a kosher market in Paris on Saturday. (Peter Dejong/Associated Press)

Of the two spouses, who lived in Bagneux near Paris, Boumeddiene may have been the more religiously observant, said Coulibaly's one-time lawyer, George Sauveur. His former client, Sauveur said, had at least six prior convictions, including three for armed robbery, before he was assigned to defend him in 2011 in a terrorism-related case, in which he said Coulibaly admitted furnishing ammunition for a planned jailbreak intended to free a radical Islamist. He was sentenced to five years.

While behind bars, authorities say, the one-time Coca-Cola employee made the acquaintance of the younger of the Kouachi brothers, Cherif, 32.

In an encounter that, in retrospect, appears astonishing, Coulibaly was among a group of people received in July 2009 by then French President Nicolas Sarkozy at the Elysee Palace for a meeting on a government program to get more young Frenchmen and women into the work force, the lawyer said.

Before the meeting, an awed and apprehensive Coulibaly, then 27, was interviewed by Le Parisien newspaper.

His temporary job at the local Coca-Cola plant in his hometown of Grigny would be over in two months, he said, adding, "if the president can help me get hired ... "

When he met Coulibaly, Sauveur said, his client said he was earning $2,600 a month— and making money on the side by dealing in Kalashnikov ammunition.

Coulibaly never talked about Islam

If Coulibaly turned to radical Islam while in prison, he hid it well, two former friends told the AP on Saturday.

One fellow drug dealer from the Paris suburb of Bretigny said Coulibaly regularly sold marijuana and hashish to high school students, and as recently as a month ago, was still dealing dope at La Grande Borne, a tough public housing estate to the south of Paris.

"He never went to prayers or talked about Islam," said the 19-year-old, who spoke on condition of anonymity because he didn't want to attract police attention. The dealer described Coulibaly as a fitness fan who worked out often and dressed in Nike shoes and athletic gear.

"I was totally shocked when I found out," the former dealer said, referring to the siege at the kosher market and the fatal shooting Thursday of a suburban Paris policewoman that authorities said was also Coulibaly's doing.

With files from CBC News and Reuters