Beijing, Dec 19 : Four people were killed and eight others injured after part of a ramp bridge in the city of Ezhou in China's Hubei province, collapsed, local authorities said on Sunday. The accident took place at 3.36 p.m. on Saturday when part of the ramp bridge spanning over an expressway collapsed, reports Xinhua news agency. Three trucks on the bridge fell off and a car was crushed under the collapsed single-column bridge, closing the two-way traffic of the expressway, the authorities said. An unknown number of people were working on the bridge when the accident occurred. Preliminary investigation showed that an overloaded truck with a weight of 198 tonnes broke into two pieces when falling off, sending two other vehicles down with it. The provincial governor and a deputy provincial governor have rushed to the scene to lead the rescue, and traffic police officers and firefighters continue to carry out emergency relief. Investigation on the cause of the accident is still underway. /IANS