One of the main suspects in an attack on a Moscow-St. Petersburg train that killed at least 26 people was described by the Interior Minister on Saturday as "over 40, stocky and ginger-haired."

Russia's federal security chief earlier said that an explosive device equivalent to 7 kg of TNT caused Friday evening's deadly derailment. Traces of explosives have been found at the scene and prosecutors have opened a criminal case on charges of terrorism.

"There is information to suggest that several people were involved," Interior Minister Rashid Nurgaliyev also told journalists. He said that a person who supplied information on the suspects was being sought.

The announcement came after Russian Railways chief Vladimir Yakunin said that a second, weaker bomb had exploded on Saturday at 2:00 p.m. (11:00 GMT) at the site of the attack, but that it had not caused any injuries.

Russia's health minister said that the death toll from the attack remained unchanged. 18 people are still missing almost 24 hours after the train went off the rails near the town of Bologoye in the Tver Region, approximately halfway between the capital and St. Petersburg. 96 people were injured.

Russian President Dmitry Medvedev has instructed the Interior Ministry to "keep the situation under control," adding that the "situation is tense as it is."

A similar derailment, also caused by a blast, occurred on the same route in August 2007, injuring 60 people. While two residents of the mainly Muslim North Caucasus region of Ingushetia were arrested in connection with that attack, prosecutors said it was planned by former soldier Pavel Kosolapov, a one-time associate of late Chechen warlord Shamil Basayev.

The blast has raised fears of a resurge of terrorist attacks in the Russian capital and other major cities. Russia was hit hard by terrorism in the 1990s and the early years of this decade, but major attacks have been confined to the volatile North Caucasus region since 2004.

MOSCOW, November 28 (RIA Novosti)