MOSCOW — A second person has died in southwestern Russia following an explosion on a city bus that also injured another 17 people, officials said Friday.

Health authorities in Voronezh, a city of 1 million residents about 450 kilometers (280 miles) south of Moscow, said two people died in a hospital from injuries they sustained in the explosion.

Another 14 people remained hospitalized Friday and three were undergoing treatment at home, AP reported.

Authorities said Thursday’s explosion in Voronezh was caused by leaky gas equipment on the bus and no trace of chemical explosives was found.

Russia’s top criminal investigation agency has opened a probe for possible charges of unsafe consumer services. But the company that operated the bus said the vehicle had a diesel engine and no gas equipment.

The National Anti-Terrorist Committee says that all options are being considered and experts continue to analyze fragments of the bus. — Agencies