SHENZHEN, Guangdong - Just five days after a boy was killed and 30 people were injured in a Beijing subway crush caused by an escalator malfunction, at least two passengers were hurt in a similar incident at Shenzhen Metro Line 4's exit on Sunday night.

"I fell backwards from about 10 steps' height," said 50-year-old Zeng from a hospital wheelchair, as she described what happened to the French-made CNIM escalator.

Zeng bled from the nose and received scratches on her face, shoulders, hands, legs and knees. She said the escalator was going up before the accident and that she and her husband were the only people injured.

A witness surnamed Jiao, who claimed to have taken video at the scene, said that at 9:16 pm the escalator at the Qinghu Station suddenly ran backward and trembled as the people on it fell down.

"It was exactly like what I saw on TV from Beijing Zoo Station's accident: a malfunction or something caused the rising escalator to reverse," said Jiao, referring to the earlier tragedy involving an OTIS type 513MPE staircase.

"I heard Zeng and her husband saying: 'What happened to the escalator? Why is it running backward?' Then somebody pressed the emergency button to stop the escalator.

"She (Zeng) was lucky as she was only about one-third up the ascending escalator. It wasn't up too high," said Jiao. "It wouldn't be a simple skin injury if she'd gone higher."

Jiao said there were about two to three people on the escalator when the accident happened. They all fell down but Zeng was the most seriously injured. Some local media reported four casualties.

According to Xinhua News Agency, Xiao Ping, spokesperson with the Shenzhen branch of the Hong Kong-based Mass Transit Railway (MTR) Corporation that operates Line 4, said the exact number of the injured and the cause of the accident were under investigation.

"The injured have been taken to hospital and doctors said they were free of serious injuries," said Xiao.

However, in a later media release on Monday morning, Hu Ruihua, deputy operations manager of MTR Shenzhen, said the escalator did not reverse its direction during the incident.

"Various factors contributed to the accident, but one thing is sure, there's nothing wrong with that escalator," he said. Hu also mentioned that the couple (Zeng and her husband) were carrying heavy items in their hands at the time.

"It (the escalator) only stopped when the emergency button was pressed, there's no wrong direction involved."

The initial results by Shenzhen Institute of Special Equipment Inspection and Test showed that the driver unit, handrail speed and emergency button on the escalator had functioned normally.

"The escalator's anti-reversal function has also been checked; it's OK," said Kong Zenghua from CNIM.

This was the third incident on the 20.5-kilometer-long Metro Line 4 since it started full operations on June 16. Hu Ruihua said the last two accidents were caused by pushing and shoving from the crowds rather than any equipment problem. There were no casualties in the previous accidents.

Shenzhen opened three new metro lines and extended its existing two at the end of June. The number of riders almost doubled within a month.

"Our average daily traffic volume was 600,000 people for May while this figure rose to 1.1 million on June 25, three days after the opening of Line 5 and three days before the full operation of lines 2 and 3," said Zhao Penglin, deputy secretary-general of Shenzhen government, which is in charge of the city's transport.

An escalator at Shanghai's Metro Line 3 also stopped on Monday morning. The escalator was produced by Xizi OTIS, a Hangzhou-based joint venture supported by investment by OTIS.

No casualties were reported. Maintenance staff later said the incident was caused by a passenger's luggage hitting the escalator's switch, according to local media.

Shanghai halted 22 OTIS 513MPE escalators in its metro system on Friday after the country's leading quality watchdog ordered the use of all escalators that are of the same type as the one in the Beijing tragedy to be suspended.

Shenzhen Metro halted 340 such escalators for inspections on Saturday.