Metro train derails in Moscow

• NEW: Moscow health officials say 160 are injured; 42 are in critical condition


• Emergencies minister says death toll is now 20, according to state media


• Three metro train cars derailed in a tunnel during rush hour, ITAR-Tass news agency reports


• The cause of the derailment is not clear

Moscow (CNN) -- The death toll in a Moscow metro derailment Tuesday now stands at 20, according to the state-run ITAR-Tass news agency, citing Russia's Emergencies Minister Vladimir Puchkov.

The Moscow health care department gave a slightly lower figure, saying 19 were confirmed dead.

Another 160 people are injured, of whom 129 are hospitalized, it said. Of those, 42 are in critical condition.

The derailment took place during morning rush hour in the Russian capital. Three metro train cars derailed in a tunnel, ITAR-Tass reported.

More than 200 people have been evacuated, the Emergency Ministry said on its website.

Dozens of ambulances arrived at the scene, along with three BK 117 helicopters, to help shuttle the injured to hospitals, according to ITAR-Tass.

It was not clear what caused the derailment, but the head of Moscow's Transportation Department said it was not a terrorist attack.

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CNN's Alla Eshchenko reported from Moscow, and CNN's Holly Yan wrote from Atlanta.