RFE/RL’s Russian Service correspondent in Tolyatti, Sergei Khazov, arrived at the scene shortly after the blast. "Today, at 7:17 a.m. local time, an explosion occurred at a bustling crossing of Karl Marx and Yury Gagarin streets in the central part of Tolyatti where a passenger bus blew up," Khazov reported.
Russian television showed footage of a long green bus with its windows blown out and roof partly ripped off. Paramedics were caring for people with bloodied faces and legs. The explosion was so strong that windows on nearby residential buildings were also said to have been shattered.
Khazov, citing officials from the Ministry of Emergency Situations, said the bus was on its regular morning route when the explosion hit. “Officials from the Prosecutor's Office and FSB [Federal Security Service] are working on the scene," he added.
Tolyatti, located on the Volga River more than 1,000 kilometers southeast of Moscow, is home to Russia's biggest automaker, AvtoVAZ. Organized crime groups fight regular turf battles in the city and gangland killings have occurred frequently.
Investigators are trying to determine the cause of the explosion but police sources already say they suspect terrorism. Vladimir Artyakov, the governor of the Samara region where the city is located, also said that the "main suspicion is moving towards terrorism."
Russian officials are often quick to blame bombings and similar incidents on Chechen militants, whom they have been battling for several years.
ITAR-TASS reported that the force of the explosion corresponded roughly to the power of 1 kilogram of the explosive TNT, or the power of several hand grenades.
Adolf Mishuev, a explosives expert, told the Russian Service that such an estimate matched his own assessment. "It looks credible,” he said. “A maximum of some 2 kilograms have been used, a minimum or 1 or 1 1/2 kilograms of TNT."