Victims of a sudden escalator failure at Beijing Zoo Station, on subway Line 4, await rescue on Tuesday morning. Witnesses say the escalator suddenly reversed directions, sending passengers tumbling down the steps. Photo: CFP

The escalator at Exit A of subway Line 4's Beijing Zoo Station suddenly reversed directions on Tuesday morning at 9:36 am, leaving one dead and four out of another 30 injured passengers in critical condition.

A woman in her 50s surnamed Han and her sister-in-law, surnamed Chen, were on the escalator when Han said she heard a sound like gears malfunctioning. Suddenly, the escalator reversed directions at free-fall speed, she said.

"I was standing at the rear of the escalator, which was bringing us up to the exit," Han told the Global Times. "Then the escalator went backward and the people in front of me fell on me."

Han suffered scratches and a bloody nose. Imprints of the escalator steps could be seen on her blood-stained arm.

"Blood was all over the escalator," she said.

Chen has high blood pressure and was still in shock.

"I heard a woman's voice shouting 'Save my child!' And I just overheard a doctor saying that the child died," said Chen, who was resting in the intensive-care unit of Peking University People's Hospital, where most of the victims were taken. Each had a yellow swatch of cloth pinned to their clothing to distinguish them from other patients.

The first ambulance arrived at the hospital at almost 10 am, according to a witness who refused to give his name.

"Police vehicles also came, so I thought there had been a fight, but then four or five more vehicles loaded with patients arrived, and an ambulance driver told me that about 30 people were injured," the witness told the Global Times.

Police and security guards immediately cordoned off the north end of the emergency department, where the injured were brought in for treatment.

A machine covered with a beige cloth was installed over a bed in a corridor blocked off by security guards. The machine is used to disinfect patients' beds, according to the witness.

"A 13-year-old boy has passed away," he said.

An emergency department doctor confirmed the boy's death on condition of anonymity.

A nurse at the reception desk of the emergency department told the Global Times that the People's Hospital received 24 injured passengers, four with serious injuries. Two children under age 10 had already been transferred to the Beijing Children's Hospital.

Those with slight injuries were brought to a single-floor building outside the emergency department to be questioned by police.

Subway Line 4 is operated by the Beijing MTR Corporation, a joint venture of the Beijing Infrastructure Investment Co Ltd, Beijing Capital Group and the Hong Kong-based MTR Corporation.

Beijing MTR employees were standing in the hospital yard at 12 pm, but they refused to say what they were doing or to comment on the accident.

According to a press release issued on Tuesday afternoon by Beijing MTR, the malfunctioning escalator was manufactured by Otis Elevator Company and was examined for maintenance on June 22. Subway Line 4's 10 Otis escalators are examined every 15 days in subway Line 4 stations, the release said, and all have been put out of service since the accident.

Beijing MTR will cover all victims' medical costs and will arrange compensation after the cause of the accident is determined, stated the press release, which also acknowledged that one passenger had died.

The case is under investigation, and the government has ordered subway system operators to eliminate safety hazards and ensure smooth operations, the Xicheng district government announced on its official microblog.

The Beijing Bureau of Quality and Technical Supervision's preliminary inspection found that the direct cause of the accident was damage to spare parts that resulted in the drive chain slipping, according to a Beijing Youth Daily Weibo post last night.

Otis' Beijing branch has already sent employees to investigate the accident, Li Mingjie, a public relations officer of Otis China based in Tianjin, told the Global Times on Tuesday evening, adding that it was still premature to talk about compensation.

"We will handle the case according to the investigation results," Li said.