MAPLE RIDGE, B.C. - A lawyer for some of the 492 Tamils who arrived in British Columbia last month is suggesting federal agencies are trying to drag out the identity checks on the migrants, thereby keeping them in jail longer.

Shepherd Moss, counsel for some of the migrants, told an Immigration and Refugee Board hearing Thursday that federal officials haven't been clear on exactly what documents they need to see for individuals to be set free.

Moss said one of his clients arrived with a national identity card, but the Canada Border Services Agency has asked to see more documents.

Once those documents are obtained, more documents may be requested.

"The (Minister of Public Safety) is not undertaking reasonable efforts unless he puts all of his cards on the table at the outset and tells these men what they have to do in order to prove their identities," Moss said.

"If the minister proposes to draw this process out by throwing out new obstacles at every detention review, then that would be unreasonable."

Thirty-day detention reviews began this week for 380 men jailed at the Fraser Regional Correctional Centre in Maple Ridge, B.C., east of Vancouver.

In all but one of the cases, Canada Border Services Agency argued the men should be kept in custody because their identities have not been confirmed, nearly a month after the MV Sun Sea docked at CFB Esquimalt.

Moss represented a man Thursday morning who was one of many Tamils to board the vessel with his Sri Lankan national identification card. The cards are outfitted with distinct security features.

The man, who can't be named because of a publication ban, has been asked to provide additional documentation.

But even once those documents are obtained, it remains unclear when he will be released from detention.

A CBSA official said Wednesday some cases may take "several months."

"If he supplies genuine documents and that's going to satisfy the minister, then the minister should tell him that that's the case," Moss said, adding it's difficult to co-operate when one doesn't know what that co-operation entails.

The border services agency is processing primary documents like the national identification cards, in B.C., but even when those documents are confirmed, other certificates might have to be verified overseas.

CBSA hasn't said when that process might be complete.

It has said the process is moving somewhat slower because 492 migrants arrived at the same time.

Identity assessments have been completed for 40 of the migrants, but none have been released from custody. One is being held on security grounds.

A number of ripped identification documents were found on board the ship, CBSA has said. They included one birth certificate, one death certificate and two Sri Lankan national identification cards.

Border services also found passport pages and pieces of birth certificates on the vessel, sparking concerns some migrants might have been trying to hide their identities. CBSA has not specifically accused any of the migrants of trying to do so.

Lynda Mackie, the refugee board's adjudicator, ruled Thursday that Moss' client will remain in custody until his next hearing in one month.

Mackie said Moss' arguments were valid, but might have been premature since the migrants arrived Aug. 13 in a very large group.

She expressed hope the government is moving as quickly as it can on many fronts as possible.

"The more forthcoming the government is, the more you'll be encouraged to co-operate fully with them in establishing your identity," she told the migrant.

Thirty-day detention reviews will continue for the men at the correctional centre Friday.

Two 30-day reviews have been conducted for the women who were on board the MV Sun Sea. The rest will begin Monday.