PARIS, France (AFP) – Nearly half of the 2,300 sailors who were aboard France’s aircraft carrier Charles de Gaulle and support craft when a coronavirus outbreak occurred at sea have tested positive for the virus, the defense minister said Friday, April 17.

With 2,010 tests conducted so far, 1,081 have come back positive, Florence Parly told parliament.

Of the total, 545 sailors had coronavirus symptoms and 24 were being treated in hospital, including one receiving intensive care, she said.

Those who tested negative were in quarantine.

Last week, it was decided to bring the Charles de Gaulle home 10 days early from a deployment in the Atlantic after some crew members showed coronavirus symptoms.

The carrier with some 1,700 crew had helicopters and fighter jets on board and was accompanied by two frigates – one for aerial defense and the other an anti-submarine vessel.

The origins of the outbreak remain a mystery. The crew of the carrier, on a three-month deployment, had not been in contact with any outsiders since a stopover in Brest in northwest France from March 13 to 16.

The virus is thought to have a two-week incubation period from infection to a positive test. The virus was first detected on the aircraft carrier on April 7.

“We don’t know if the virus was already present on board before the March 13 stopover,” said Parly.

The Navy on Thursday denied allegations by a sailor that the commander of the Charles de Gaulle had asked for the mission to be cut short already during the Brest stop.

The vessel had been deployed in the Atlantic as part of a NATO exercise after taking part in Operation Chammal that seeks to contain Islamic State in Iraq and Syria.