The death toll in Tuesday's derailment on the Moscow metro now stands at 21, the Russian health ministry says.
Scores were injured, some seriously, when a packed commuter train braked abruptly between stations in the west of the city in the morning rush hour.
Some of those hurt were carried out of the tunnel on stretchers, with the most serious cases airlifted to hospital.
The cause of the crash - one of the worst incidents ever on the metro - is reported to be a power surge.
The train derailed between Slaviansky Boulevard and Park Pobedy (Victory Park) stations in the west of the city.
Some 50 people were in a serious condition, the Itar-Tass news agency reported, quoting a health official.
"The train slowed down abruptly, the lights went off, and then there was a spark of fire and smoke. We were blocked in," one passenger told Russian TV.
Another, quoted by Reuters news agency, said: "We were trapped and only got out by some miracle. I thought it was the end. Many people were hurt, mostly in the front carriage because the cars ran into each other."
More than 1,100 people were evacuated
The packed commuter train was travelling from the north-west of Moscow to the city centre at the time of the crash.
The BBC's Artyom Liss, in Moscow, says the tunnel where crash happened was built about 10 years ago.
Critics accuse the authorities of spending too much on extending the metro system, and not enough on maintenance, our correspondent says.
President Vladimir Putin, who is currently visiting Brazil, has ordered a criminal investigation into the accident.
Park Pobedy is the deepest metro station in Moscow, 84m (275ft) underground, which made the rescue operation particularly hard.
No foreigners were among the injured, the Interfax news agency said.
Militant attacks on Russia's railways and transport networks have killed dozens of people in the past, but the emergencies ministry said there was no suspicion of such a cause in this case.