The MV Sun Sea, carrying 492 Tamil migrants from Sri Lanka, was escorted into the harbour at Esquimalt, B.C., on Aug. 13. (DND)

Some of the nearly 500 Tamil migrants who travelled to British Columbia inside a cramped cargo ship had no idea that once they finally set foot on Canadian soil they could be kept behind bars for weeks or even months.

Five of the migrants, all women, participated in an Immigration and Refugee Board hearing in downtown Vancouver on Thursday.

The women, who are being housed at a Vancouver-area correctional facility, were ordered to remain in custody for at least another week. Their next hearing is scheduled for Aug. 26.

Despite the fact that some of the migrants who were aboard a ship that arrived in B.C. last year spent months in custody, not everyone on the latest vessel was aware they could be detained for so long.

The women thought they would be able to explore the country soon after they arrived, said Malini Dyonisius, a lawyer representing the female migrants at Thursday's hearing.

"When they come to Canada, they think the next day they [can] go and see Canada and enjoy," Dyonisius said in an interview. "They are now taken aback. I told them, 'It's not going to be a week or two. It might take months."'

Some detainees pregnant

The federal government has said it won't hesitate to strengthen Canada's human smuggling laws if it prevents future ships full of migrants from arriving in the country's waters.

Ottawa has not provided specifics, but Public Safety Minister Vic Toews has suggested Canada will work more closely with its allies to prevent future ships from even setting sail.

A translator and lawyers representing the federal government and Tamil migrants sit before an immigration adjudicator in Vancouver. (Jane Wolsak/CBC)

David Poopalapillai, spokesman for the Canadian Tamil Congress, said some of the migrants weren't aware of what awaited them in this country.

"They're totally new to Canada, totally new to the system. You can't blame them," he said of the migrants.

He said the refugee process can move much quicker when a migrant arrives by himself or in a small group.

"They don't realize when somebody comes one or two in a group, or 490 in a group, it's a huge difference," he said.

The MV Sun Sea, carrying 492 migrants from Sri Lanka, docked at CFB Esquimalt near Victoria on Aug. 13. The ship was intercepted off Vancouver Island a day earlier.

The migrants were processed by the Canada Border Services Agency (CBSA) and then ferried to correctional facilities near Vancouver. Refugee board hearings began this week.

Two of the women at Thursday's hearing were pregnant.

Documents controversy

All five wore dark green sweaters and grey sweat pants. Their black sneakers were individually numbered on the heel.

Dyonisius asked the Ministry of Public Safety to prioritize the cases of the pregnant women, whom she said are still relatively early in their pregnancies.

Members of the Canada Border Services Agency are seen wearing surgical masks as they board the MV Sun Sea. (Jonathan Hayward/Canadian Press)

A ministry lawyer told the refugee board it's best to keep the women behind bars while their identities are confirmed.

The CBSA has been criticized for storing identification documents inside two utility trailers without connecting the records to their individual owners.

A CBSA spokeswoman said in a written statement Thursday the evidence has been properly handled at all times.

As of Thursday, just over 300 detainees had been through their mandatory detention review. All were detained on the grounds of establishing their identity.