A section of tunnel has collapsed on a Moscow metro train, Russian emergency services have reported.
Emergency workers brought passengers out of the tunnel
Some reports say the collapse caused a fire in the train.
The incident occurred on a section of subway between Sokol and Voikovskaya stations in north-west Moscow, an Emergency Ministry spokesman said.
Viktor Beltsov, the spokesman, said that all passengers had been evacuated and there were no casualties. Services were suspended on the affected line.
The collapse occurred at 1437 local time (1137 GMT) on a train travelling towards the city centre, officials said.
A concrete slab from the tunnel's supporting structure is thought to have pierced the third carriage of the train.
Preliminary reports say the collapse was caused by workers at street level driving a pillar into the ground to set up an advertising billboard.
The workers had not been properly authorised to do the job, the city's public prosecutor's department said.
Correspondents say the accident highlights the dilapidated state of the city's aging underground system.