Photo taken on Dec. 25, 2017 shows a view of the scene of a crash involving a bus that drove into a pedestrian underpass in Moscow, Russia, on Dec. 25, 2017. (Xinhua/Bai Xueqi)

MOSCOW, Dec. 25 (Xinhua) -- At least four people were killed and nine others were injured after a bus drove into a pedestrian underpass in western Moscow on Monday, Russia's Interior Ministry said.

The Interior Ministry's Moscow division said in a statement that considered causes of the incident include "failure of the driver to control the vehicle or a malfunction of the vehicle."

The driver has been detained and is now being interrogated by police, it said.

Currently, investigators and traffic police are working at the scene.

"According to the driver, the bus, while being at a bus stop, suddenly began to move independently despite the driver's attempts to stop it because the braking system did not work," the Russian Investigative Committee said in a separate statement.

The committee has launched criminal proceedings on the grounds of "providing services that fail to meet security requirements and violation of traffic and vehicle operation rules."

Sergei Sobyanin, mayor of Moscow, tweeted, "We rendered urgent assistance. I sympathized with the relatives and friends of the victims."

Earlier in the day, media outlets and the Interior Ministry's Moscow division said five were killed in the incident.