Agence France-Presse reports that three sailors have died of food poisoning on an oil tanker traversing the Channel between Britain and Europe, French maritime authorities said Wednesday.

The captain of the Marshall Islands-flagged Arionas reported the deaths overnight, French officials said, adding that the source of the food poisoning was not known.

French officials have sent a helicopter with two gendarmes and a doctor for a preliminary investigation. More gendarmes would be sent later to question the crew.