PARIS (Reuters) – Nearly 700 sailors assigned to the French aircraft carrier Charles de Gaulle's naval group have tested positive for the coronavirus, the armed forces ministry said on Wednesday.

The ministry said 1,767 mariners, nearly all from the Charles de Gaulle itself, had been tested and results showed at least 668 to be infected with the new coronavirus. Results are still not in from a third of the tests.

“Thirty one personnel are today in hospital,” it said in a statement. “More tests are being carried out.”

The carrier, which had most recently been taking part in exercises with northern European navies in the Baltic Sea, arrived home in Toulon two weeks earlier than expected after about 40 crew members showed signs of COVID-19 symptoms.

Sick crew members had been placed under strict medical observation on board the nuclear-powered carrier and a team equipped to carry out the first tests airlifted to the vessel.

Crew from the Charles de Gaulle and the frigate Chevalier Paul were now in confinement within their naval base, while the pilots of the carrier's warplanes and helicopters were also in quarantine.

The navy chief had ordered an investigation, the ministry said.

The Charles de Gaulle set sail for the eastern Mediterranean on Jan. 21 to support French military operations against Islamist militants in Iraq and Syria, before deploying to the Atlantic and then the Baltic.