The Cap Blanc sank on Tuesday, after it capsized about four nautical miles off Newfoundland's southeast coast. (Courtesy Roger Etcheberry)

Canadian Coast Guard boats continued the search Wednesday evening for the crew of a French cargo ship that sank off the coast of southern Newfoundland.

Four men are missing from the Cap Blanc, which capsized just off Newfoundland's southeast coast. The vessel had been heading back to home port in St-Pierre-Miquelon with a full load of road salt.

The vessel sank a few hours after Canadian search and rescue crews found it capsized around noon on Tuesday about four nautical miles southeast of Marystown, on Newfoundland's Burin Peninsula.

Coast Guard officials confirmed to CBC News that first responders reported there were signs of life in the capsized vessel. Search and rescue crews were unable to stabilize ship, however, in time to further investigate. The vessel sank shortly thereafter.

Jean-Pierre Berçot, the prefect of St-Pierre, told RFO — the public broadcasting station in St-Pierre — that said divers heard a response from inside the Cap Blanc while they knocked on the vessel.

Nonetheless, Berçot said that residents of the tiny islands are not ready to abandon efforts.

"We don't have the right to give up the search," Berçot told RFO. "We don't have the right to give up hope."

Berçot said the divers did not have time to rescue anyone, because the boat sank shortly thereafter.

A Canadian Coast Guard vessel, the George R. Pearkes, searched the area overnight but found no sign of the crew.

The vessel had three lifeboats. It's not known whether the crew were wearing survival suits. On Wednesday, coast guard officials estimated that the crew could survive for about 36 hours if they were wearing appropriate survival gear.

The crew had been expected to arrive in St-Pierre at about 3 a.m. Tuesday.

Two other Canadian vessels and a French vessel that happened to be in Newfoundland will be participating in the search on Wednesday.

The air search effort, though, has been scaled back. Two Cormorant helicopters and a military plane from Nova Scotia had been involved on Tuesday, although the air search on Wednesday now involves a single Cormorant.

The crew of the Cap Blanc did not issue a distress call, and the search only started after the vessel was reported overdue Tuesday.

Residents anxious

The wife of Capt. Jean-Guy Urdanabia, a respected mariner in the community, declined an interview with CBC News Tuesday, but said family members are very anxious.

And as the search continues, Joseph Enguehard, a local resident of St-Pierre, said everyone in the community is anxious as well.

"St-Pierre is a small community, so everyone knows everyone," he said. "I would say it would be a dreadful shock."

In the meantime, Christian Delage, a former captain of the Cap Blanc and a friend of the missing sailors, had his own theory as to what caused the vessel to capsize.

He said he believes that there were high side winds that caused the load of salt on the small boat, which less than 40 metres in length, to shift to its right side because high waves were coming from the left.

Delage said he thinks the cargo moved and the crewmembers couldn't balance the boat, an incident that happened so fast that they didn't time to send a mayday or put their survival suits on.

The Cap Blanc was one of two vessels used to ship freight between Newfoundland and St-Pierre-Miquelon. The Cap Blanc's run usually was between Fortune and St-Pierre.