Initial efforts to separate two vessels that collided off Corsica have failed.
The 17,900-gt Cotunav ferry Ulysse (built 1997) steamed into Cyprus Sea Lines' 5,018-teu boxship CSL Virginia (built 2005) on Sunday morning, spilling 600 tonnes of fuel in a slick stretching 25km.
Euronews reported that more experts, including divers, have travelled to the scene to assess the impact in the hull of the container vessel.
"The idea is to avoid worsening the situation," a spokesman for the French regional maritime authority told Euronews.
Bad weather has been hampering operations.
French vice-admiral Charles-Henri du Che told reporters that an estimated 200 cbm of fuel spilled into the sea on Sunday. All but 40 cbm had been recovered by Wednesday, he added.
The ferry was en route from Genoa to Rades in Tunisia.
CSL Virginia was not carrying any cargo.
A simulation using AIS data by MarineTraffic shows the ferry maintaining a straight course and ploughing into the boxship at 19 knots.
