U.S. experts concerned about Iran's handling of crash probe

U.S. and Canadian accident investigators are uncertain how much access they will get to evidence that could prove whether Iran shot down a Ukrainian passenger jet, and there were fears Friday that the probe might already be compromised by the removal of wreckage from the crash site.

Clues to whether the Boeing 737 was brought down by an Iranian anti-aircraft missile, as the U.S. and its allies allege, could be extracted from its black box recorders, which could capture the sound of an explosion, and from an examination of its pieces for such things as shrapnel holes, burn marks or explosive residue.

All 176 people aboard were killed when the American-built jetliner went down in flames on the outskirts of Tehran during takeoff early Wednesday, hours after Iran launched a barrage of missiles against U.S. forces. The dead included at least 63 Canadians.

Iran on Friday denied one of its missiles downed the jetliner, and it challenged the West to produce its evidence.

Television reports on Friday indicated that debris had been cleared from the crash site, leaving the area to scavengers to pick over. If the wreckage was indeed moved, some clues might have been lost unless the Iranians took careful steps to preserve evidence.

“Normally you would very carefully map out a debris field. If a missile struck the airplane, you would expect to find some pieces of it and residue of the explosive,” said Steven Wallace, former head of the accident-investigations office of the Federal Aviation Administration.

Jeff Guzzetti, a former accident investigator and FAA official, said he would not be troubled by a cleanup if the Iranians first documented the exact location of every large piece, stored them properly and agreed to let investigators from the U.S. and other countries inspect...