French authorities say four men have been detained in an investigation into a failed attack last year on a suburban Paris church.

The Paris prosecutor's office said the four men were arrested separately Tuesday in suburbs northwest of Paris. France's LCI television reported they may have provided logistical help to chief suspect Sid Ahmed Ghlam.

Authorities say Ghlam, a 25-year-old Algerian, planned to attack a church in Villejuif and is also suspected in the killing of a woman nearby. The computer science student was arrested in April 2015 after apparently shooting himself by accident and has been jailed on preliminary charges since then.

Investigators have said Ghlam received instructions from someone, possibly in Syria, before implementing the plot.