Beijing's police and quality supervision authorities have launched a joint investigation into Sunday's escalator accident at a downtown department store that killed a 9-year-old boy.

The boy became stuck in an ascending escalator at Xinyidai Department Store on Xidan commercial street in the heart of Beijing at around 12:30 p.m., a spokesman with Beijing public security bureau said.

The spokesman said his bureau had joined the local quality watchdog to probe the accident.

Witnesses said the boy, who was taking the escalator from the 5th to the 6th floor by himself, had poked his head beyond the railing, got stuck between the ascending escalator and the wall, and died instantly.

The boy's mother was a vendor at the store and was too busy to keep an eye on him, said Hong Liang, a store manager.

Hong said the store has 30 escalators and 10 elevators. "All of them receive routine maintenance and are operating normally."

He said the store management would cooperate with authorities in the investigation and was yet to reach a compensation deal with the boy's family.

The department store was still open after the accident, though the killer escalator was cordoned off.

In July last year, a 13-year-old boy died and 30 others were injured when an ascending escalator at the Beijing Zoo Station on Subway Line 4 suddenly reversed. A subsequent inspection showed the escalator was not well maintained and had a design defect.

The accident triggered a nationwide safety-check campaign on escalators and elevators.

(Xinhua News Agency January 29, 2012)