Crash investigators from Canada have visited the site of an Iranian plane disaster in which 57 Canadians died and will examine the wreckage later on Wednesday, Transport Minister Marc Garneau said.

The investigators have not yet been granted access to the flight and cockpit recorders, Garneau told a news conference.

Iran has issued visas to a team of Canadian officials, including two specialists from the Transportation Safety Board who are in Tehran to probe how and why Iran on Jan. 8 shot down a Ukrainian airliner, killing all 176 people on board.

"They have visited the crash site. ... Today two investigators will examine the wreckage," Garneau said.

"What we have been told by the Iranians is that we will be allowed to participate in not only the decoding of the (black) boxes, but also the analysis," he said. "We're standing by at the moment to find out where that is going to happen. We have not had that signal."