A Maltese-registered cargo ship has been impounded and its captain questioned following the sinking of a French trawler off the Alderney coast.
A criminal investigation is being carried out by French authorities
The Sichem Pandora is thought to have been in the area where the Kleine Familie disappeared on Thursday.
The chemical carrier was on its way from Tunisia to the Netherlands with 15 on board, when it was escorted to Dunkirk by French Maritime Police.
The search for five missing fishermen has now been called off.
A French naval minesweeper is continuing to look for wreckage on the sea bed, which is 200ft (60m) deep in the area near the Casquets reef where the 50ft (15.2m) wooden trawler sank in the early hours of Thursday morning.
French authorities had earlier said the Kleine Familie had probably been involved in a collision.
Thursday's major air and sea search included French coastguards, military craft, lifeboats from Alderney and the Channel Islands Air Search plane.
The chemical carrier was escorted to Dunkirk
A criminal investigation is now also under way, led by BEAmer, the French marine accident authority.
The president of the Lower Normandy Fisherman's Association said the Kleine Familie was a good boat, and the skipper had been sailing for about 25 years.
He said it was a catastrophe for the port of Cherbourg, where the trawler came from.