Iran admitted Tuesday that the anti-aircraft missiles its armed forces fired at a Ukrainian passenger plane earlier this month were made by Russia.

Iran's Civil Aviation Organization, which is leading the investigation into the deadly mishap, said in a preliminary report that the missiles were launched from the TOR-M1 air defense system. In 2017, the Associated Press says, Iran received the delivery of 29 TOR-M1 units from Russia under a contract worth an estimated $700 million.

However, the report said “the impact of these missiles on the accident and the analysis of this action is under investigation.”

When the missiles hit the aircraft on Jan. 8, they caused an explosion. The fire generated from that blast, however, appears not to have reached inside the cabin, the report added, citing the condition of debris later recovered from the crash.

A Russian Tor-M1 missile system similar to those supplied to Iran in 2006 is photographed in an undisclosed location in Russia. (AP)

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The TOR short-range air defense system, code-named the SA-15 by NATO, was designed during the Soviet era to shoot down aircraft and precision-guided weapons.

It is mounted on a tracked vehicle, and carries a radar and a pack of eight missiles. Each vehicle can operate independently. The system has a range of up to 7.5 miles and can hit aerial targets at altitudes of up to about 19,700 feet.

Tor missiles explode near their target, taking it down with shrapnel that devastates engines, fuel tanks and other vital components, the Associated Press says.

All 176 passengers and crew on board the plane died in the crash, officials said. (AP)

Iranian officials have offered contradictory remarks on whether they'll send the plane's flight data and cockpit voice recorders abroad to be analyzed. The preliminary report by the Civil Aviation Organization said Iranian officials had asked French and American authorities to send them “up-to-date equipment” to pull the data in Iran.

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Over the weekend, Hassan Rezaeifar, the official leading the investigation, was quoted by the state-run IRNA news agency as saying “the flight recorders from the Ukrainian Boeing are in Iranian hands and we have no plans to send them out.”

The same official was quoted by the Tasnim news agency on Saturday saying the recorders would be sent to Ukraine, where French, American and Canadian experts would help analyze them.

The Associated Press contributed to this report.