The government is raising security questions during detention hearings for a number of the 76 Tamil migrants who arrived off the West Coast on a decrepit little freighter earlier this month.

The men, at least three of whom crewed the Ocean Lady across the Pacific from Sri Lanka until it was intercepted in Canadian waters on Oct. 17, are undergoing their second and third mandatory detention hearings before the Immigration and Refugee Board.

Details of the hearings are under a publication ban because the men are being treated as potential refugee claimants, though not all have made formal claims.

While the board approved detention initially based on questions about their identities, counsel for the Canadian Border Services Agency has begun raising public security as grounds for further detention.

As of Friday, hearings of at least a dozen claimants were adjourned because border services' lawyers "introduced a new ground for detention and disclosed supporting documents that needed to be reviewed by the parties in order to prepare for the hearing," said board spokeswoman Melissa Anderson.

A rarely-used section of the Immigration and Refugee Protection Act allows the immigration minister to request detention in order to "inquire into a reasonable suspicion that they are inadmissible on grounds of security or for violating human or international rights."

There are concerns the migrants may include those who may have links to the Tamil Tigers, the military arm of the Tamil separatist movement that's been at war with the Sri Lankan government for decades.

The Tigers are banned in Canada as a terrorist organization because, among other things, they used suicide bombings to attack targets in the Sinhalese-dominated parts of the country.

The Sri Lankan army crushed the rebellion last May but officials of the Canadian Tamil Congress have said the young men chose the risky ocean journey because Tamils are still persecuted and it's nearly impossible for them to come to Canada legally.

By late Friday, the board had wrapped up 15 more mandatory seven-day detention reviews -- for a total of 63 -- ordering continued detention in all cases.

Most remain in custody because identity documents have not been verified. The migrants get another mandatory review within 30 days.

The hearings are taking place at the board's downtown Vancouver offices, though often their lawyers are taking part via telephone link from Toronto.

Those whose families haven't hired lawyers are being represented by duty counsel from the B.C. Legal Services Society.

Hearings have gone well into the evening as the men face seven-day and 30-day detention reviews.

Dressed in red prison T-shirts and pants, often with long underwear underneath, the men shuffle to their hearings in leg shackles and handcuffs.

The board ordered one migrant released last Friday under restrictions.