At least 20 people were killed when a metro train derailed in Moscow on Tuesday, according to the state-run ITAR-Tass news agency, citing Russia's Emergencies Minister Vladimir Puchkov.
The Moscow health care department said another 160 people are injured, of whom 129 are hospitalized
Forty-two of those hospitalized were in critical condition.
The incident took place during the morning rush hour in the Russian capital.
Three metro train cars derailed in a tunnel, the state-run ITAR-Tass news agency reported.
More than 1,100 people have been evacuated, according to The Associated Press.
Dozens of ambulances arrived at the scene, along with three BK 117 helicopters, to help shuttle the injured to hospitals, according to ITAR-Tass.
It was not clear what caused the derailment, but the head of Moscow's Transportation Department said it was not a terrorist attack.
The subway train derailed near the Park Pobedy station, which, at 275 feet deep, is the subway system's deepest station, according to The Associated Press.
The derailed train was stuck between two stations, and a rescue operation to evacuate survivors went on for more than seven hours, according to the AP.
Mayor Sergei Sobyanin said service between the two stations where the derailment occurred would probably be suspended for two days, according to the AP.
While the Moscow subway has been the target of several terrorist attacks in recent years, it's been decades since the train system has had a deadly accident, according to the AP. Officials are ruling out terrorism in this case.