An accident last Friday at the Otis Elevator factory in Guangzhou has an employee on crutches after an operational error involving an overhead crane sent a box weighting several hundred kilograms plummeting onto the worker's leg, one of the company's suppliers told the Daily Economic News.

The mishap comes just months after a malfunction of an Otis escalator in a busy Beijing subway station that left a 13-year-old boy dead and 28 others injured.

The anonymous source said the American company's headquarters this week sent staff to the Guangzhou subsidiary to inspect the facilities, which recently passed review by another batch of inspectors.

An unnamed employee at the factory on Wednesday confirmed the accident with a Daily Economic News reporter visiting the site. "It was a crane operator," the worker said. "He was very seriously injured. His leg broke on the spot. I was there. He was about to lift the glass when a collision occurred. The goods fell off. Fortunately, there were other things that blocked the falling box. It didn't hit the man directly. I heard his waist was also hurt."

Other employees near the factory also confirmed the incident.

Company suppliers said inspectors from Otis headquarters had previously passed the Guangzhou factory. But this week, inspectors will be coming back for a review following European standards.

If the Guangzhou site fails to pass the test, it faces losing its "silver" safety certification, the second-highest of three safety grades given by the firm. Company suppliers said a downgrade to "bronze" would impact the factory's sales substantially.

Didier Michaud-Daniel, president of Otis Elevator, praised the company's Guangzhou factory on a visit in June this year, just days before the Otis escalator accident in Beijing.