MOSCOW, August 13. /TASS/. The investigation thinks that a technical issue was the main cause of a bus explosion in Voronezh, a source in law enforcement told TASS on Friday.

"At this stage, the main version of the incident is a technical one: the vehicle’s equipment failure or changes in its construction. A rapid analysis did not detect any traces of explosive substances," the source said.

He added that at this moment the preliminary investigation established that the explosion occurred in the gas tank area on the left side of the bus.

The blast occurred on a shuttle bus in Voronezh not far from a shopping center on Thursday evening. According to preliminary data, 18 people were injured, at least three of them are in a serious condition, one woman was killed. Authorities have specified that the bus was running on diesel fuel and had no gas equipment onboard.

A criminal case has been opened in accordance with Article 238, Part 2 of the Russian Criminal Code (the provision of services that do not meet safety standards). Chairman of Russia’s Investigative Committee Alexander Bastrykin ensured the case is under control of the agency’s headquarters. On his instructions, experienced investigators and forensic experts of the agency’s headquarters were sent to Voronezh for practical aid in the investigation.