MOSCOW, April 30. /TASS/. /TASS/. An electrical device short circuit is the cause of the fire that broke out at the central research institute of the Aerospace Defense Forces in Tver in central Russia, killing over 20 people, a source in law-enforcement agencies told TASS on Saturday.

"The preliminary circumstances and the cause of the fire have been established. The blaze was caused by an electrical device short circuit in a room on the second floor when no one was present there," the source said.

A late call to the fire-fighting service could have caused large fire and, as a result, heavy smoke, he specified. "This version also finds its confirmation," the source said.

There were 175 people inside the building at the time when the fire started and 54 of them were rescued from the premises swept by the blaze while 98 others went out into the street themselves. The bodies of 22 people were found in the course of the efforts to clear the rubble and the search for those missing continues, he said.

The fire at the central research institute of the Russian Aerospace Defense Forces broke out on an area of 2,500 square meters on April 21. A criminal case has been opened under Part 3 of Article 219 of Russia’s Criminal Code (‘Violation of the Fire Safety Rules that Entailed the Death of Two and More Individuals Through Negligence’).

The case is being probed by military investigators.