Immigration officials have released a pregnant Tamil woman from protective custody in British Columbia, making her the first of nearly 500 migrants who arrived on Canada's west coast.

The woman, whose name is protected by a publication ban, was released Tuesday from the immigration holding facility in the Vancouver suburb of Burnaby where she has been held since arriving in Canada.

Lawyers for the woman argued she should be freed in order to care for her three young children, while federal officials had argued that she should remain in detention until they could establish her identity.

But Michael McPhalen, of the Immigration and Refugee Board, ruled that the Canada Border Services Agency's request was not reasonable.

Since refugee board hearings for the boatload of Tamils began, the agency has said it's prioritizing cases involving women and children.

In ordering the woman released however, McPhalen said he couldn't imagine a case that was a higher priority.

The woman, who left on the MV Sun Sea with her husband and three other children, had a Sri Lankan national identification card that had been ruled authentic.

She requires treatment for an ongoing health issue and one of her children has a head wound.

Melissa Anderson, a spokeswoman for the refugee board, said the woman was not ordered to pay a bond before being released. She must report to the nearest border services agency by Sept. 16.

Her husband is still being held with the remainder of the men from the ship at a correctional centre in nearby Maple Ridge.

The woman's release comes as Immigration Minister Jason Kenney acknowledged that the government was aware of an impending influx of Sri Lankan Tamil refugees well before the MV Sun Sea arrived.

Ottawa was not caught off guard by the arrival of the cargo ship and it's 492 Tamil passengers, Kenney said Tuesday. The ship was part of a wave of human smuggling the Canadian government was warned would be en route following the end of a 30-year civil war in that country.

"We are not surprised with what happened. We were tracking the Sun Sea voyage for three months before its arrival in Canada," Kenney told reporters during a trip to China. "Frankly, I think we recognize we need stronger tools to address that."

On Tuesday, The Globe and Mail cited documents that suggest Stephen Harper's government was warned of a rush of Sri Lankan Tamil refugees eight months ago, well before the Sun Sea cargo ship arrived in August.

Those documents, obtained by Vancouver immigration lawyer Richard Kurland, included a report dated Jan. 12, 2010 that warned the Canadian government that the end of Sri Lanka's 30-year civil war would create a significant challenge for Canadian immigration.

"The economic and social issues caused by the civil war coupled with a relatively wealthy international Tamil Diaspora results in a large push/pull factor for human smuggling and trafficking," according to the report by Canadian officials, as quoted in The Globe.

"Some have called this a perfect storm as overseas friends, family and relatives appear willing to fund irregular migration operations. As Canada has over 250,000 former Sri Lankan nationals living in the country, Canada will be a target destination."

Sources told The Globe that Harper's cabinet will be presented with options for discouraging vessels of refugee claimants next week. Those measures could include intercepting ships at sea and instituting harsher penalties on the smugglers.

Those aboard the Sun Sea have been detained as their identities are confirmed. The Immigration and Refugee Board of Canada ordered the release of a pregnant Tamil migrant on Monday, making her the first to be released from detention.

Kenney used his trip to China to push for foreign support in curbing human smuggling to Canada. He appealed to the governments of countries such as China, India and the Philippines – common source countries of Canadian refugees – to help control illegal immigration.

"This is a real concern for us, because we don't want people paying $30-$50,000 to get on a rickety boat and go across the Pacific Ocean, endangering their lives and being indentured to some human smuggling network," Kenney said.

"We have got to send a strong message, and the government is considering measures that would send a very clear signal, to the human smuggling networks that we will not tolerate this kind of illegal immigration."

Kenney told reporters to "stay tuned" on what measures the government will take to crack down on the problem. He added that he was discouraged by the public's general backlash to immigration following the Sun Sea controversy.