Debate continued to swirl Tuesday around the fate of dozens of Sri Lankan men who showed up on B.C.'s coast last month on a rusting vessel.

The way Ottawa sees it, the 75 young Tamil refugees still in detention at the Fraser Correctional Centre need to stay there because they may pose a national security risk.

"We will insist that their detention continues as long as there is any doubt about people constituting a security threat to Canada," Immigration Minister Jason Kenney told reporters Tuesday. "The Canada Border Services Agency and the RCMP continue to do diligent work in researching the background of these individuals and how they got to Canada. Safety of Canadians comes first."

This week, at a detention hearing for one of the refugee claimants, border officials revealed that trace amounts of explosives were found on some clothing and aboard the "Ocean Lady."

The government says the vessel may have been used by the Liberation Tigers of Tamil Eelam to transport guns and munitions in the three-decades-long civil war in Sri Lanka.

But lawyer Daniel McLeod, who is representing a half-dozen of the refugees, said he's reviewed the government's evidence and found it lacking.

"It's very skimpy. In fact, I'm surprised," he told CTV News.

McLeod says it's possible the ship was used for transporting explosives, which would explain the residue on the ship.

But "that doesn't make any of the 76 people on that ship in any way involved" with the Liberation Tigers, he said.

"No evidence has been presented that would implicate any of the 76 Tamil young men on that ship."

McLeod suggested Kenney was milking the issue for political gain.

"I think maybe he is positioning himself for an eventual run at the leadership. This is a hot-button issue, it gets headlines. It makes him look alike a law-and-order guy," he said.

Neither the Canada Border Services Agency nor the immigration minister will confirm the quantity or on whose clothing the trace explosives were found.

But Kenney said if the government concludes that any of the individuals was involved in organized crime or terrorism or terrorist organizations, they will be deemed inadmissible.

If that is the case, the Tamils will be sent back to Sri Lanka, where their Canadian supporters say they will face persecution -- or worse.

With a report from CTV British Columbia's Peter Grainger