The discovery of scores of graves in people-smuggling camps in Malaysia is casting a shadow over President Barack Obama's signature trade deal as U.S. lawmakers consider punishing trading partners that are soft on human trafficking.

Just as Obama's drive to win fast-track trade negotiating authority for the deal entered its most sensitive stage in Congress, Malaysian police announced the discovery of 139 graves in jungle camps used by suspected smugglers and traffickers of Rohingya Muslims from Myanmar.

"This new information is very alarming," said Sen. Robert Menendez, referring to the burials in Malaysia, which would be a signatory to a massive Pacific trade pact that Obama wants to complete this year.