The Thai cargo ship MV Sun Sea is expected to be steered toward CFB Esquimalt in Victoria. (CBC)

Canadian officials have boarded a cargo ship believed to be carrying hundreds of Tamil migrants off the B.C. coast, military sources tell CBC News.

In a day of conflicting reports from various government sources about the vessel being boarded, the Prime Minister's Office said a combination of naval and RCMP officers would likely board the vessel at approximately 10 p.m. ET, although the report of the actual boarding came about 30 minutes sooner.

Sailors and police officers were then to take control of the vessel and steer it to CFB Esquimalt, where it would be docked.

Government sources told CBC News that the ship was first visually identified by military vessels at 2:30 p.m. ET and that the vessel entered Canadian territorial waters at 5:30 p.m. ET.

"Errant information" announcing the vessel had been boarded at 4:30 p.m. ET was passed on by officials in the Canada Border Services Agency, the sources said.

Earlier Thursday afternoon, Public Safety Minister Toews had said personnel from HMCS Winnipeg boarded the Thai vessel MV Sun Sea after it changed course and started heading toward Port Alberni, B.C.

Toews had said, "the Winnipeg attempted to hail the Sun Sea several times and, after establishing communications, the vessel declared that it had refugees on board."

The ship, now off the coast of Vancouver Island and travelling slowly through fog, is believed to be carrying Tamil migrants from Sri Lanka.

Toews said there are 490 migrants aboard the ship, and the vessel's operator has declared them to be refugees — but Toews said some of the people on the ship are "suspected human smugglers and terrorists."

Toews said the best way to deal with such people is once they enter Canadian waters.

"Intervening on the high seas brings certain legal obligations and a number of legal problems, and so it’s better to intercept them, I’m advised, inside of Canadian territorial waters."

Human smuggling 'despicable crime'

Toews said human smuggling is a despicable crime and such criminals elsewhere in the world are watching Canada's response to this incident. He said the government will send a message "loud and clear" that human smugglers will be prosecuted.

The "terrorists" Toews referred to are believed to be members of the Liberation Tigers of Tamil Eelam, which have been outlawed in Canada as a terrorist group since 2006.

The migrants will likely be taken to two correctional facilities in Maple Ridge, east of Vancouver. Any children on board will likely be put into the care of B.C.'s Ministry of Children and Family Development.

A cluster of white tents was set up Thursday morning at CFB Esquimalt in Victoria, where the migrants will be processed as they come off the boat.

Canadian officials have released little information about the boat or those believed to be on board, but staff at Victoria General Hospital have reportedly been advised that they might have to treat a large number of sick people when the ship arrives.

With files from The Canadian Press