ROSTOV-ON-DON, March 16. /TASS/. The preliminary cause of the fire inside the building of the FSB Border Guard Directorate in Rostov-on-Don was a short circuit in the electrical wiring inside, the region’s Governor Vasily Golubev said on his telegram channel on Thursday.

"According to preliminary findings, the fire was caused by a short circuit in the electrical wiring inside. The spreading fire caused explosions of containers with fuel and lubricants," he wrote.

Golubev added that two walls had collapsed.

The fire spread to an area of 800 square meters, 14 vehicles and 63 Emergencies Ministry fire-fighters are involved in extinguishing the blaze.