A powerful bomb went off inside a bus carrying students and workers on Wednesday morning in the city of Togliatti in South Russia. Eight people were killed and over 50 more were injured in the incident. Police are probing the incident as a terrorist attack, but no group has claimed responsibility for it at the time of publication.

The explosion hit the bus at 8:17 a.m. local time during rush hour. Initial reports from police experts said that the explosion was caused by a homemade bomb with the explosive power of two kilograms of TNT. Seven people were killed on the spot and one man died in an ambulance on his way to the hospital.  Most of the wounded were standing at a bus stop when the explosion occurred and suffered concussions and cuts from broken glass.

Investigators immediately suspected that the blast was a terrorist attack. Bombings, often carried out by suicide attackers, were frequent in Russia several years ago, but have not happened lately. As experts started to work with the remains of the explosive device they quickly established that it had been a homemade bomb similar to one used by young Russian nationalists in Moscow in an attack on a Vietnamese café in 2006. Investigators also said that the bomb exploded inside the bus, approximately 120 centimeters from the floor. They said that there were no metal fragments that terrorists usually put inside their explosive devices to increase their efficiency.

All this data indicates that the blast was not a deliberate terrorist attack, but rather an accidental discharge. 

Prosecutors have launched criminal cases into murder of two or more people and into terrorism.

On Thursday morning the police reported that they had the first suspect in the case. However, they did not name the man and did not say whether he was alive or dead. They only reported that the suspect's apartment was searched and that certain objects found there had matched the fragments found on the scene of the crime. "We have all grounds to suggest that we have established the very person who had willingly or unwillingly committed the actions that lead to the bus explosion," the head of the investigation committee of the Prosecutor General's office Alexander Bastrykin told reporters. 

"There can be two explanations here, either it was a terrorist attack, not necessarily of nationalist character or careless handling of the substances that could for some reason result in an explosion," he said. The official said that the explosive device was not triggered with a radio controlled fuse and that it was unlikely carried by a suicide attacker.

The Stavropol region governor announced a day of mourning for the dead on Thursday.

Togliatti is a city with a population of about 700,000 on the Volga River in South Russia's Stavropol region. The main enterprise in the city is the Avtovaz car plant which produces the popular Lada car. The crime situation in the city has been bad since the 1990s when mobs got the car business under their control. Some Russian media suggested that the explosion was a part of a gang war, but the police refused to comment on it.

After the blast the regional police launched a major anti-terrorist operation. Officers with sniffer dogs are searching all public transport including minibuses before they allowed to carry passengers. Private cars and trucks are also checked randomly. All police has been put on special alert.

Apart from this, police are probing false reports about several new explosions that appeared in the media immediately after Togliatti bus blast.