MOSCOW (AP) — A Russian military plane crashed in annexed Crimea, killing six crew and 23 passengers on board, Russian news agencies reported in the early hours of Wednesday, citing the country's Defense Ministry.

The An-26 military transport plane was carrying out a scheduled flight over the Crimean peninsula, which Russia illegally annexed from Ukraine in 2014, the reports said. The military lost contact with the plane around 6 p.m. on Tuesday.

Russia's top investigative agency, the Investigative Committee, said a total of seven crew members and 23 passengers were aboard the plane. It wasn't immediately clear from official statements if one crew member survived the crash.

Russian news agency Interfax quoted the Defense Ministry as saying that they believe the crash was caused by a technical malfunction and that there was no “damaging interference” with the plane.

The plane crashed into a cliff, sources at the site of the crash told state news agencies Tass and RIA Novosti.

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.

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