BILOXI, Miss. �?Three Canadian warships that were in the U.S. Gulf Coast as part of Canada's hurricane aid mission are on their way home, less than a week after they arrived in the region.

The HMCS Athabaskan, HMCS Ville de Quebec and HMCS Toronto left Biloxi, Miss., on Sunday morning, while the Canadian coast guard ship Sir William Alexander and other personnel stayed behind.

The three warships arrived in Pensacola, Fla., last Monday, where they dropped off humanitarian supplies before heading to Biloxi.

In Biloxi, a small city of about 50,000, Canadian sailors went ashore and were used largely as manual labour.

They spent their time cleaning up and repairing public buildings such as schools, hospitals and a navy retirement home, all damaged when hurricane Katrina devastated the region two weeks earlier.

When the three warships and the coast guard cutter were deployed, navy officials said the mission could last as long as a month.

But a navy spokesman said Sunday that the ships and personnel were called back because they were no longer needed in the region.

"No one ever said that they would be there for that exact time frame," Mike Bonin said in Halifax.

"They were there as long as they were needed to be there. There's no sense for them to be there if there's no requirement for the ships to be down south."

On Thursday, a U.S. official had said the Canadian mission would be gearing down because civilian agencies and workers would soon be able to take over.

There were other signs the mission wouldn't be as extensive as first thought.

On Wednesday, the coast guard ship was told not to unload all of its relief supplies when it was in Pensacola, since some of the items such as tents were no longer required.

And by the second and third day that the sailors were on the ground in Biloxi, they seemed to be running out of things to do.

Canadian navy officials weren't sure when the ships would return to port in Halifax, saying it will depend on the weather and how fast the ships travel along the U.S. East Coast.

The Sir William Alexander, several Canadian dive teams and a group of structural engineers were to remain in the area for an unspecified amount of time.

The dive teams were expected to continue clearing debris from the region's waterways so commercial traffic can access the area's ports.

The Sir William Alexander had been re-establishing buoys and other navigational aides in the waters off Biloxi and Gulfport.

Bonin said the coast guard ship could also assist in heavy lifting, since it is equipped with a large crane.

"They're going to do any tasks that are requested of them," he said.

The coast guard cutter and the three warships carrying 1,000 personnel left Halifax harbour on Sept. 6.

The deployment was part of Canada's hurricane aid mission, dubbed Operation Unison.

The Category 4 hurricane Katrina hit the region on Aug. 29.

The death toll along the Gulf Coast so far has reached almost 900, including more than 600 in Louisiana.

The U.S. government has already awarded reconstruction contracts totalling hundreds of millions of dollars.

The entire recovery is expected to cost well over $100 billion US.

Meanwhile, up to 180,000 evacuees could start returning home to New Orleans this week. The area was flooded when its protective levees gave way.

But the plan has been criticized by the head of the U.S. Katrina effort as "extremely problematic."