The derailment took place at about 8.35 a.m. between the Slavyansky Bulvar and Park Pobedy metro stations on the city's Blue Line, The Moscow Times reported citing a statement on the Moscow Metro website.
Slavyansky Bulvar metro station was temporarily closed as rescuers attended to the victims.
An emergency situations ministry spokesperson Tuesday afternoon put the toll at 19.
He said 12 bodies were still inside the wreckage of the metro. From the bodies that had been recovered, four were identified as those of males and three of females, he said.
A decrease in the electric voltage running through the tracks of the metro led to the derailment, the report said citing a spokesman for Moscow's Emergency Situations Ministry.