MOSCOW, Russia—A second person has died in southwestern Russia following an explosion on a city bus that also injured another 17 people, officials said Friday. Authorities said Thursday’s blast on the bus in the city of Voronezh was caused by leaky gas equipment. No trace of chemical explosives was found, they said. The Investigative Committee, 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 and insisted it was in good technical condition. The National Anti-Terrorist Committee said all options were being considered and experts continued to analyze fragments from the bus. 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 …