At least eight people are dead and 56 have been injured following a bomb blast on a bus in the Russian city of Togliatti. VOA Moscow Correspondent Peter Fedynsky reports that local authorities are treating the explosion as a possible act of terrorism.

The bomb exploded at a busy intersection in downtown Togliatti, a city of about 700,000 people and home to AvtoVaz, Russia's largest car maker. Most of the injured were college students, and a small child is reported among those killed.

A spokesman for the local rescue service, Andrei Derbenev, says the explosion shattered windows on nearby residential buildings. Law enforcement officials say the blast had the equivalent of up to two kilograms of TNT.

Officials are ruling out a gas tank explosion, because the bus is reported to have run on diesel, a less volatile fuel. They are also trying to learn if the bomb was carried on board by a passenger, whether it was attached on the floor or underside the bus, or whether it was laid in its path.

Vladimir Artyakov, the governor of Samara Province, the region of southern Russia that includes Togliatti, says the basic premise of an investigation into the blast is terrorism.

The governor's spokesman, Ivan Skrylnik, told VOA the explosion involves three legal charges.

Skrylnik says a criminal case has been launched involving terrorism, premeditated murder, and illegal production of an explosive device.

Togliatti has a reputation for violence involving organized crime groups that compete for influence in the city. The governor's spokesman declined to comment on whether any such group may have been involved in the blast.

Samara province has not been known for terrorist attacks of the kind that occur in the Caucasus region more than 1,000 kilometers southwest of Togliatti.

But the Interfax News Agency quotes a source close to the investigation as saying authorities do not exclude the possibility that Wahabbi or other Islamic extremists may be involved in the blast. Samara province has a substantial Muslim population.

President Putin has sent a top federal investigator from Moscow to help conduct the inquiry.