Russian intelligence officers said Saturday that the derailment of a luxury train that killed at least 26 people and injured dozens more was caused by a bomb blast.

The Nevsky Express, en route to St. Petersburg from Moscow, derailed Friday night near the town of Bologoye on the border between the Tver and Novgorod regions.

A derailed railway carriage is seen near the town of Bologoye, Russia, Nov. 28, 2009. The Nevsky Express, enroute to St. Petersburg from Moscow, derailed here Friday night. Russian intelligence officers said Saturday that the derailment of a luxury train that killed at least 26 people and injured dozens more was caused by a bomb blast. [Lu Jinbo/Xinhua]

The 14-car train was carrying 653 passengers, including three foreigners, and 29 crew members. The Chinese embassy in Moscow told Xinhua that it has not received any reports of any Chinese citizens being injured in the derailment.

The derailment was caused by a homemade bomb equivalent to seven kg of TNT, Federal Security Service chief Alexander Bortnikov said.

"Indeed, this was a terrorist attack," said Vladimir Markin, a spokesman for the Investigative Committee of the Prosecutor General's Office.

Some detached parts of a derailed train are seen on the site of the accident near the town of Bologoye, Russia, Nov. 28, 2009.[Lu Jinbo/Xinhua]

A crater 1.5 meters in diameter and 0.7 meters deep was found at the scene.

"Presumably, an explosive device was detonated on the train route," Markin said.