CHONGQING - An under-construction bridge that collapsed in southwest China's Chongqing Municipality on Saturday morning was caused by an unstable beam on a floating crane, local authorities said.

An initial investigation found that the beam, known as a cantilever, fell and impacted steel cofferdams which supported a pier of the bridge, according to the publicity department of Fengdu county.

The bridge was being built across the Yangtze River in Fengdu county.

The No. 4 pier of the under-construction bridge collapsed and was submerged in water at about 10:30 am. At least two people are missing and another two are slightly injured as a result of the accident.

The injured are being treated in a local hospital. Search and rescue work is still under way.