MOSCOW -- Russian investigators launched a terrorism probe yesterday into a bomb blast that derailed an express train from Moscow to St. Petersburg, injuring more than 60 people traveling on one of the country's busiest rail routes.
The explosion occurred late Monday near the city of Novgorod, about 300 miles northwest of Moscow. Investigators said they believe a homemade bomb placed underneath the tracks was detonated by remote control as the Nevsky Express train passed with 251 people aboard.
Russian investigators issued composite sketches of two suspects. The head of Russia's main security agency suggested that terrorists threats were still acute and that police agencies were prepared to bolster security and surveillance nationwide before parliamentary and presidential elections in December and March.
Nikolai Patrushev, director of the Federal Security Service, told a national anti-terrorist committee meeting in Moscow that "the threat of extremism and terrorism has not been completely eliminated."
The bomb blast tore a three-foot wide gap in the rail line 100 feet before a bridge. But because the train was traveling at 80 mph, it had enough momentum to cross the bridge before derailing, Russian authorities said.
Although no one was killed, the blast unnerved a nation that has seen a lull in terrorist activity outside the volatile North Caucasus region in the past couple of years.
The bomb blast near Novgorod mirrored the attack on a train traveling from Grozny to Moscow on June 12, 2005, in which a remote-controlled bomb planted on a stretch of track near the capital derailed the train and injured 42 people. In April, two Russian ultranationalists were convicted of engineering the attack.
No one had claimed responsibility for the blast near Novgorod as of last evening. In the past, separatist rebels fighting for Chechnya's independence from Russia have been linked to a litany of terrorist attacks.
The Nevsky Express is popular with foreign tourists, although there were no reports of any foreigners injured in the blast.
Russian authorities said that of the 60 people injured, 25 were hurt seriously enough to be hospitalized. Five people were listed in critical condition.
Alex Rodriguez writes for the Chicago Tribune. The Associated Press contributed to this article.