DUBAI (Reuters) - Iran said on Sunday it was trying to analyze the black boxes of a Ukrainian airliner that its military shot down this month, denying a report that a decision had been taken to send the voice and flight data recorders to Ukraine.

Canada, which had 57 citizens on the flight in which all 176 people aboard were killed, said on Sunday there were still no firm plans for downloading the recorders. Ottawa and other capitals have called for the black boxes to be sent abroad.

The Jan. 8 plane disaster has heightened international pressure on Iran as it grapples with a long-running dispute with the United States over its nuclear program and its influence in the region that briefly erupted into open conflict this month.

The military has said it downed Ukraine International Airlines flight 752 in error in the aftermath of tit-for-tat strikes by the United States and Iran. But authorities delayed admitting this, prompting days of protests on Iran’s streets.

“We are trying to read the black boxes here in Iran. Otherwise, our options are Ukraine and France, but no decision has been taken so far to send them to another country,” Hassan Rezaifar, a director in charge of accident investigations at Iran’s Civil Aviation Organization, told state news agency IRNA.

Rezaifar had been quoted by Iran’s semi-official Tasnim news agency on Saturday as saying the black boxes could not be decoded in Iran and would be sent to Ukraine after Kiev’s repeated requests. IRNA also reported on Sunday that the official had made similar comments a day earlier.

It was not immediately clear what prompted Rezaifar to backtrack.

The Boeing 737-800 was en route from Tehran to the Ukrainian capital. Most of those on board were Iranians or dual nationals.

Canadian Foreign Minister Francois-Philippe Champagne said he wrote to his Iranian counterpart, Mohammad Javad Zarif, on Sunday to urge the boxes be sent quickly to Ukraine or France.

FILE PHOTO: The crate containing purportedly the two black boxes recovered from the crashed Ukrainian airliner, Boeing 737-800, is seen in this still image taken from a video, in Tehran, Iran January 10, 2020. IRIB VIA WANA/Handout via REUTERS

Canada’s Transportation Safety Board said two of its investigators left Tehran on Sunday after a six-day visit during which they examined the wreckage.

Iranian investigators were “cooperative and helpful” but said there were still no firm plans on how and when the black boxes would be downloaded, it said in a statement.

PAYING RESPECT

Ukraine has previously said it expected the recorders to be handed over, while Canadian Prime Minister Justin Trudeau has said France was one of the few countries with the ability to read information on the recorders.

France’s air accident agency BEA said on Saturday it was awaiting an official request for assistance.

The bodies of 11 Ukrainian victims were brought home on Sunday in a ceremony at Kiev airport. Ukrainian Foreign Minister Vadym Prystaiko said that “bereaved families and the whole nation have an opportunity to pay their respects”.

The plane was brought down when the military was on high alert in the tense hours after Iran launched missiles at U.S. targets in Iraq in response to the killing of a top Iranian commander in a U.S. drone strike on Jan. 3 in Baghdad.

Iranian President Hassan Rouhani has called the downing an “unforgivable error” and promised to hold those responsible to account. The Revolutionary Guards also issued profuse apologies, as protesters raged against the Guards and the clerical system that the elite force was set up to protect.

The Islamic Republic’s supreme leader, Ayatollah Ali Khamenei, said on Friday that “some tried to use it as an excuse to overshadow the martyrdom of our great commander” Qassem Soleimani, the powerful general killed in the U.S. strike.

The death of Soleimani, portrayed as a national hero at home but seen as a dangerous enemy in the West, led to huge mourning ceremonies in Iran, followed just a few days later by angry protests over the plane disaster.

Tension between Tehran and Washington has escalated since 2018, when the United States withdrew from Iran’s nuclear pact with world powers and reimposed sanctions.

Tehran reduced its commitments to the 2015 pact, under which Iran agreed to scale back nuclear work in return for sanctions relief. European states triggered a dispute mechanism last week over the violations, a step that could lead to U.N. sanctions.

Parliament speaker Ali Larijani said Iran would review its cooperation with the U.N. nuclear watchdog, the International Atomic Energy Agency, should it face “unjust” measures.