A spokeswoman for the Paris prosecutor's office says one of the four suspects detained over an explosion and beheading in southeast France has been released, while the suspected assassin isn't speaking to investigators.

Yassine Salhi, a truck driver with a history of radical Islamic ties, remains in custody Saturday in Lyon a day after allegedly crashing a truck into an American-owned chemical warehouse and hanging his employer's severed head on a factory gate.

Paris prosecutor's office spokeswoman Agnes Thibault-Lecuivre said investigators have not turned up any motive or possible foreign connection. Under French anti-terrorism laws, he can be held up to four days before either being released or handed preliminary charges and locked up.

Salhi's wife and sister remain in custody, while another man was released without charge.