The site of the UIA plane crash outside Tehran / REUTERS

The IRNA news agency quoted Tehran military prosecutor Gholamabbas Torki as saying that the recorder was sent to France, without elaborating, The Associated Press reported on June 29.

Read alsoIran to send black boxes from downed Ukrainian airliner to France – media

He said the recorder was "physically damaged" and that the data could only be recovered with "sophisticated" technology.

He said Iran's own experts were unable to acquire the necessary converter because of U.S. sanctions.

Iran accidentally shot down the Ukraine International Airlines (UIA) Boeing 737-800, killing all 176 people aboard, after mistaking it for an incoming missile. Iran had been bracing for a counterattack after launching missiles at U.S. bases in Iraq in response to the killing of its top commander, Gen. Qassim Soleimani, in a U.S. strike earlier in January.

Since, then it has been in negotiations with Ukraine, Canada and other nations that had citizens aboard the plane, and which have demanded a thorough investigation.

Iran initially blamed the crash on technical problems and only acknowledged shooting down the plane days later.