Moscow is observing a day of mourning after Tuesday’s metro crash which killed more than 20 people and injured 150 in the Russian capital.
People have been gathering at the Park Pobedy station where the train derailed, to pay their respects.
The flag on the roof of Russia’s parliament, the Duma, has been flying at half-mast.
State investigators say they have arrested two metro workers suspected of safety breaches.
Russia’s federal Investigative Committee said a track supervisor and an assistant had been detained. It is thought they failed to properly monitor work carried out on a track switch mechanism in an underground tunnel.
This resulted in the train coming off the rails, the committee said.
Hundreds of people have come forward to give blood, to help the scores who sustained injuries, many of them life-threatening.
“I was profoundly shocked by yesterday’s events, and the only thing I can do is come here today and give blood. It’s the contribution that every healthy person, who wants to help those who were injured, can make,” said Tatiana Tsivlina, a student who volunteered.
The crash, in the middle of Tuesday morning’s rush hour, was Moscow’s worst ever metro accident.
More than 1,100 people were evacuated from the train, which was stuck between two stations in Moscow’s west, in a rescue operation that lasted more than 12 hours.
Russian media have demanded a “transparent” inquiry into the capital’s transport system, and warned against finding scapegoats.
Aging equipment and spending cuts have been denounced.