Maher Arar was exonerated of any blame in Canada
The US is to investigate how its immigration service deported a Syrian-born Canadian to Syria where he was allegedly tortured.
Maher Arar was deported as a terrorism suspect from a New York airport in 2002 and it is widely accepted in Canada that he was tortured while in Syria.
Canada compensated him after exonerating him and finding the US had acted on Canadian information.
Syria denies that Mr Arar was tortured during the time he spent in prison.
He was eventually released without charge and returned to Canada, where he was awarded 10.5m Canadian dollars (US$8.9m, £4.54m) in compensation.
The head of the internal watchdog of the US Homeland Security Department said it was reviewing new information in the case, the Associated Press reports.
Inspector-General Richard Skinner told a US Congressional hearing on Thursday that the new evidence contradicted an earlier conclusion that US immigration agents had acted appropriately in deporting him.
Mr Arar was detained and questioned by US customs agents in New York's JFK airport in September 2002 while changing planes on his way back from a holiday in Tunisia.
A Canadian government inquiry accepted he had been tortured during almost a year of imprisonment.
The inquiry also took Canada's police force to task over the incident, criticising the force for spreading misleading and false information about Mr Arar.
Royal Canadian Mounted Police Commissioner Giuliano Zaccardelli later resigned, saying his force had made major mistakes.
Canada has repeatedly called on the US to drop Mr Arar from its security watch list.
The US government rarely releases information about its rendition programme, in which suspected terrorists are moved from country to country without public legal proceedings.