ST. PETERSBURG, April 4. /TASS/. The buses that duplicate the operatioin of St. Petersburg’s blue (second) line will continue working until 10am Moscow Time despite the full restoration of the underground transport, the press service of the city’s Transport Committee reported on Tuesday.

"The St. Petersburg subway resumed work completely in the morning along all lines and stations. However, buses duplicating the subway’s work will continue operation until 10 am," the press service said.

An unidentified device went off at about 14:40 Moscow time on Monday in a subway train car when the train was moving from Tekhnologichesky Institut Station to Sennaya Ploshchad Station. The Russian Investigative Committee has qualified the blast as a terrorist attack, but other versions are looked into as well.

According to the latest data provided by the National Anti-Terrorism Committee, the blast claimed 11 lives, while 51 others were injured.