Russian officials are blaming an explosion at a subway station on Monday in St. Petersburg that killed 10 people on terrorism. 

"We will do our utmost to clear up the factors that made the terrorist attack possible to rule out such cases in the future," Aleksandr Kurennoi, a spokesman for Russia's Prosecutor-General's office, told the Russian News Agency TASS

The Sennaya Square subway station was evacuated after “an unidentified device” detonated inside a train. Russia’s subway service said it closed down seven stations due to the explosion.

A reporter from The Washington Post said on Twitter that 50 people were injured in the blast.

Russian President Vladimir Putin said in a statement on television that he had been in contact with officials who “will do everything to find out the causes of what had happened," The New York Times reported

“The government, both on the city and federal levels, will do everything to support families of the victims and injured,” he said.

Putin was in St. Petersburg for a meeting with the leader of Belarus.

United Nations Ambassador Nikki Haley said in a statement that the U.S. “will stand with Russia on defeating these extremists who continue to senselessly harm innocent people."

Russian officials said they discovered a second device at another metro station, but were able to dismantle it, The Associated Press reported.

--Rebecca Savransky contributed to this report, which was updated at 2:16 p.m.