MOSCOW, December 25. /TASS/. Muscovites are bringing bouquets of flowers to the underground walkway near Slavyansky Boulevard metro station where a hair-raising road accident involving a commuter bus occurred on Monday afternoon.

The bus veered off the road and plunged into a crowded underground walkway at around 14:50 on Monday, killing four people and leaving another eleven injured. All the victims of the accident were pedestrians, a police source said.

One of those killed was a twelve-year-old girl. Also, there was an adolescent among the injured.

Investigators are considering two possible causes of the accident: a loss of control over the bus by the driver and malfunctioning of the bus.

The vehicle has been recovered from the walkway and evacuated to a specialized parking area. It has a broken windscreen and smashed windows along the left-hand side, which scraped the barrier of the walkway.

The police detained the driver of the bus.