At least eight people were killed and several other were injured after a residential building under construction collapsed in northwest China, local media reported on Sunday. The tragedy occurred on Saturday morning at a construction site in the suburbs of the city of Xi'an, the capital of Shaanxi province when a four-storey residential building unexpectedly collapsed, leaving over a dozen construction workers trapped under its debits, the media reported. Rescue works involving over 300 firefighters and medical staff continued for more than 24 hours, the media reported. According to preliminary information, a poor quality of construction materials could have been the cause for the accident, the media reported.