HARBIN - Residents from five households have been evacuated and no casualties have been reported after an apartment building cave-in early Thursday morning in Northeast China's Heilongjiang province, according to a local government source.

The collapsed apartment building is seen on this July 21, 2011 photo. [Photo/CFP]

The accident occurred at around 4:30 am Thursday, when the right side of a six-storey residential building collapsed in Nangang district of Harbin, the provincial capital.

The collapsed part involved five households, which, thanks to the time lag between previous vibrance of the building and the ensuing collapse, had been evacuated before the cave-in.

Li Sichuan, deputy head of Nangang district, said the collapse was caused by groundwork digging beside the building.