A Russian military transport plane has crashed in illegally annexed Crimea, killing six crew members and 23 passengers, according to reports from Russian news agencies early on Wednesday.

The An-26 aircraft was conducting a scheduled flight over the peninsula, which Russia seized from Ukraine in 2014, when military officials lost contact with the plane around 6pm on Tuesday.

Russia’s top investigative agency, the Investigative Committee, later stated that a total of seven crew members and 23 passengers were aboard the plane.

This left it unclear from official statements whether one crew member had survived the incident.

The country’s Defense Ministry, quoted by Russian news agency Interfax, indicated that a technical malfunction is believed to have caused the crash, ruling out any “damaging interference” with the aircraft.

Sources at the crash site, speaking to state news agencies Tass and RIA Novosti, confirmed that the plane plummeted into a cliff face.

The Investigative Committee said it has launched a criminal probe on the charges of violating flight regulations, and a search operation was underway in a mountainous forested area in Crimea.

“There was no impact on the aircraft,” TASS quoted the ministry as saying, implying that objects like missiles, drones and birds were not involved.

“The preliminary cause of the crash is a technical malfunction. A commission from the military is working at the site,” it said.

The An-26 is a Soviet-designed military transport turboprop aircraft.

The An-26 has been in service since the late 1960s and has also been used by airlines to carry freight, but the model has been involved in a number of deadly crashes over the last decade.

A Ukrainian An-26 crashed during a technical flight in Ukraine’s southeastern Zaporizhzhia region in 2022, killing one person. Another aircraft crashed on a training flight in northeastern Ukraine in 2020, killing all but one of the 27 people on board.

Eight people, including five Russians, were killed when an An-26 crashed in South Sudan in 2020. Four of 10 people on board were killed when an An-26 crashed on landing in Ivory Coast in West Africa in 2017.