The death toll in Tuesday's train derailment in Russia has been updated by the Health Ministry as six people dead and 29 injured.

"Another person has just passed away at a hospital," Moscow Region Deputy Governor Dmitry Pestov said on Tuesday. "We are looking for victims' relatives to give them our assistance," he added.

The train crash happened in the Moscow region on the railroad line between Naro-Fominsk and Bekasovo. A freight train derailed and collided into a long-distance passenger train from Moscow to Chisinau.

Vadim Andronov, a rescue coordinator, told Russian news agency Itar-Tass the death toll is likely to rise.

"One of the carriages of the passenger train was crushed by the goods train wagons," he said. "Rescuers are working to pull out injured people being crushed by the wagon."

The accident, based on initial information from the Moscow Transport Department, was caused by a broken rail.

Authorities have started a criminal investigation.

"We tried to use an emergency brake. We couldn't see anything ahead, there was lots of dust. Visibility was zero," state-run RIA news agency quoted one of the drivers of the passenger train.

The long-distance passenger train was carrying 400 people, according to the emergencies ministry. Five people immediately died in the accident.

"There are 17 emergency teams working at the scene of the accident, including six on-call paramedic brigades from the city of Naro-Fominsk, five on-call paramedic teams from Moscow, three teams from the local center of disaster medicine, four teams from the All-Russia Center of Disaster Medicine Zashchita with the Russian Health Ministry and one aerial medical team," the Russian health authority said in a statement.

Vladimir Stepanov, Deputy Emergency Minister, had ordered lists of the wounded so they can be easily monitored and ready when families ask for their whereabouts.