FONTAINES-SUR-SAONE, France — The top suspect in the beheading of a businessman that French authorities are calling a terrorist attack took a “selfie” photo with the slain victim and sent the image via WhatsApp to a Canadian mobile phone number, officials said Saturday.

French investigators were working to determine the recipient’s identity, but weren’t able to immediately confirm media reports that it was an unspecified person now in Syria, where the radical Islamic State group has seized territory, the security officials said.

The revelation added a macabre twist to an investigation that has not turned up a solid link to radical or foreign groups, but has revived concerns about terrorism in France less than six months after deadly attacks in the Paris area.

Top suspect Yassine Salhi, a truck driver with a history of radical Islamic ties, as well as his sister and wife remained in police custody in the city of Lyon, a day after he allegedly crashed a truck into a U.S.-owned chemical warehouse and hung his employer’s severed head on a factory gate, officials said.

One of the officials said the selfie was forwarded via WhatsApp, the globally popular instant messaging system owned by Facebook, to a phone number in Canada. The officials spoke on condition of anonymity because the investigation was ongoing.

Royal Canadian Mounted Police spokeswoman Josephine Laframboise had no immediate comment on the report.

No group immediately claimed responsibility. The severed head appeared to mimic Islamic State’s practice of beheading prisoners and displaying their heads for all to see, and came days after the militants urged attacks during the Muslim holy month of Ramadan. French authorities say Salhi had links to radical Salafists in the past.

Paris prosecutor’s office spokeswoman Agnes Thibault-Lecuivre said the leading suspect began speaking with investigators after first refusing to do so. She declined to provide details, but said investigators haven’t found any foreign connection.