French officials say they suspect an entire family — 11 people including a grandmother — of departing to wage jihad in Syria.

Paris anti-terrorism prosecutors opened a preliminary investigation Wednesday following the family's disappearance from their homes in Nice, on the French Riviera.

France estimates that nearly 1,000 of its residents have left for jihad in Syria and Iraq this year, and the Interior Ministry estimates that 350 are still there, with the others either on their way, leaving the battlefields or killed.

France was the first country to join U.S. airstrikes against Islamic State group extremists and has increased its monitoring of French people suspected of joining them.

Parliament is debating a bill to provide new tools to fight terrorism, including taking away passports of suspected would-be jihadi fighters.