Police have found bomb-making materials in a car park near Paris as part of an investigation into an “extremely dangerous terrorist cell” linked to an attack on a kosher grocery.
Paris prosecutor Francois Molins said the discovery in Torcy, east of the capital, led authorities to invoke a rarely used legal clause to allow them to extend questioning of 12 suspects by a day - and possibly two.
The country has been on high alert for possible terror attacks by radical Islamists after a man who claimed links to al-Qa'ida shot and killed three Jewish children, a rabbi and three paratroopers in southern France in March.
Investigators were led to the underground car park through information collected during questioning of the suspects, who were arrested in weekend raids across France in a probe of a firebombing of the grocery north of Paris last month, Mr Molins said.
It is believed the two organisers of a September 19 grenade attack in Sarcelles are in custody, he said. However, he suggested that the two people who actually carried it out could still be at large.
"When there is a serious risk of the imminence of a terrorist action in France, police custody - after 96 hours - can be extended by 24 hours," he said.
It was only the second such extension since a 2006 revision to France's powerful anti-terrorism legislation. In most terrorism cases, police can detain suspects for questioning for up to four days before preliminary charges are filed or the suspects are released for a lack of enough evidence to merit prosecution.
In Torcy, investigators recovered bags of potassium nitrate, sulphur, saltpetre, headlight bulbs and a pressure cooker - "all products or instruments useful to make what are called 'improvised explosive devices,"' Mr Molins said.
"We can say that we are clearly and objectively facing an extremely dangerous terrorist cell," he said.
On Saturday police found weapons, cash and a list of Paris-area Israeli associations after the raids conducted in eastern Strasbourg, near the Riviera resort of Cannes, and in the Paris area - including Torcy. In Strasbourg, police shot dead Jeremie Louis-Sidney, whom they suspect to be the cell's leader, after he opened fire at them with a revolver.
The suspects in custody are French and recent converts to Islam. Four of them had written wills. One was carrying a loaded gun.