OTTAWA • Canadian investigators will get access to the wreckage and black boxes of a Ukrainian jetliner downed by a missile strike last week, officials said.

"We don't fully know what the scope of our investigation will be," Transportation Safety Board (TSB) chair Kathy Fox told a press conference on Monday, adding: "There have been early signs Iran is allowing the TSB to play a more active role than is normally permitted."

Two Canadian investigators were to land in Teheran yesterday, followed by two more in the coming days or weeks. They have been invited by Iran, which is leading the crash probe, to participate in the downloading and analysis of the cockpit voice and data recorders.

They will also be allowed to visit the crash site and the wreckage of the plane that is being reassembled in a nearby hanger.

"We do know what has happened. What we don't know is why it happened," Ms Fox said before listing the questions over the crash that still need to be answered. These include whether the missile strike was intentional or not, and why the airspace was open amid heightened tensions in the region.

The Ukraine International Airlines Boeing 737 was shot down by a missile soon after taking off from Teheran airport before dawn last Wednesday, killing all 176 passengers and crew on board. Fifty-seven of the victims were Canadian.

Earlier, Canada's Foreign Minister said a Canadian-led group of nations that lost citizens in the crash would press Iran for an open and transparent investigation at a meeting in London tomorrow.

"We have convened the first in-person meeting of the international coordination and response group on Thursday at Canada House in London," Mr Francois-Philippe Champagne said on Twitter.

At the meeting, foreign ministers from Canada, Ukraine, Sweden, Afghanistan and Britain will seek to maintain pressure on Iran for full access to the investigation, as well as renew calls for transparency and accountability.

The group will also discuss seeking compensation for the families of the victims.

Washington-Teheran tensions have soared since Jan 3, when missiles fired from a US drone killed Iran's Major-General Qassem Soleimani near Baghdad's airport.

Iran responded with a barrage of missiles at two US bases in Iraq, inflicting no casualties in what was seen as an attempt to prevent an escalation. But hours later, an Iranian Revolutionary Guard unit mistakenly shot down the Ukrainian passenger jet in what President Hassan Rouhani called a "human error".

AGENCE FRANCE-PRESSE