French police who broke up a suspected terrorist cell have discovered bomb-making material in an enclosed parking lot in suburban Paris, the state prosecutor said Wednesday.

Francois Molins said police investigators recovered items including potassium, sulfur, saltpeter and a pressure cooker as well as two weapons in the lot in the town of Torcy, east of Paris.

They were led there by information from interrogations carried out since the arrest of a dozen suspects in cities across France at the weekend, he said, adding that authorities are extending the detention of the suspects for 24 hours beyond the normal limit of 96 hours because of the seriousness of the case.

"We can say that we are clearly and objectively facing an extremely dangerous terrorist cell," Molins said. He added that it was only the second time since 2006 that the law allowing the extension of custody in such circumstances had been invoked.

The weekend arrests — during which one suspect was killed by police who returned fire after he shot at them — were put in motion by evidence gathered following the firebombing of a kosher grocery story in suburban Paris in September.

Police found weapons, cash and a list of Paris-area Israeli associations during the raids.

It remains uncertain whether those suspected of directly carrying out the grocery store attack have actually been apprehended.

Molins said at the time that all the arrested suspects were French and recent converts to Islam. Four of the men involved in the raid had written wills. One was carrying a loaded gun when arrested.