MOSCOW, April 21. /TASS/. A number of people killed in a fire at the Central Research Institute of the Aerospace Defense Forces in the Russian city of Tver climbed to seven, at least 25 sustained injuries, a source in the local emergencies service told TASS on Thursday.

"We confirm a number of seven deaths at the moment," the source said adding that the number of casualties may increase. The source stated earlier that five people were killed in the fire killed and more 25 injured.

According to emergencies services, the fire currently engulfed a total area of 2,500 square meters before it had been localized by rescuers.

The ministry involved a Mi-8 helicopter, which dropped at least 10-tank loads of water in order to put out the fire.

According to earlier reports, some people suffered injuries caused by fumes, while others received injuries after jumping out of windows to escape the fire.

The blaze erupted on a second floor of the building and then engulfed the area of about 1,000 square meters. According to preliminary reports, a short circuit failure was the cause behind the reported incident.