The spill was spotted on Friday by the French navy during an exercise carried out from the Solenzara air base in Ventiseri, Corsica, according to maritime officials.
By Saturday morning, officials had detected two oil slicks over 19 nautical miles (35 kilometers), which were drifting about 5 nautical miles from Corsica’s east coast, between Aléria and Solenzara, France’s Mediterranean Maritime Prefecture said in a statement.
Pollution experts concluded the spill was heavy-grade oil and likely the result of a “degassing,” which involves the release of any gases left in fuel tanks or crude oil tanks after they’ve been emptied.
“The size and nature of the products involved do not allow for natural dilution and require specific anti-pollution units and equipment,” the prefecture said, adding that “the pollution (is) currently drifting towards the coast.”
“Some materials are visible up to 800 meters from the coast,” Christine Ribbe, a prefecture spokeswoman told French radio station France Inter on Saturday morning. “We fear that some of this pollution will reach the Corsican coast today,” she added.
France’s environment minister Barbara Pompili said she would visit the site on Saturday with maritime minister Annick Girardin.
Pompili said France’s maritime police had opened an investigation into the spill. “Thank you to the professionals mobilized to fight against this environmental scourge,” Pompili said on Twitter.
Authorities in the Haute-Corse department, the northern part of Corsica, have blocked access to the beaches in the towns of Aleria until Ventiseri and told residents “not to touch collect any oil clumps they find on beaches.” Fishing was also prohibited in the same areas on Friday night.
