Two excavators were seen in operation on the rooftop of a building in Zhengzhou, Henan Province, on Wednesday, which caused local residents to worry over their safety.

The building is located at an intersection of the city where a new metro line will pass through in 2018, and has 12 stories in total, making it around 30 meters high. In the vicinity of the construction are several blocks of residential areas.

The two excavators were reported to be lifted up by cranes and dismantled three floors. 

A worker, identified by his surname, Zhou, said to China Foto Press (CFP) that it was not the first time that excavators had operated on rooftops in China, and explained that this building cannot be ruined by blasting because there were many residences, nor was it dismantled by workers due to numerous reinforcing bars.

According to the construction company, they are following its predecessors in Shanghai and Chongqing with the premise that they have thoroughly studied the structure of the building.

A metro station will be set up after the building is torn down.