At least five workers were killed and seven were injured when a stone bridge under construction collapsed Monday in northwest China's Shaanxi Province, a local official said Wednesday.

The Zhangjiahe Village Bridge, in Qingjian County of Yulin City, collapsed at about 11:30 a.m. Monday, said Yang Huaizhi, vice county head.

Construction of the arched bridge, which is 29.5 meters long, 6meters wide and 12 meters high, began on June 5 and is expected to be completed on Sept. 5, with an investment of 300,000 yuan (43,914 US dollars) from the county government.

An initial investigation blamed the accident on the project contractor firm, which changed the original construction plan without the approval of authorities, said Yang.

The project contractor, Shaanxi Yulin Hongtai Construction Engineering Co. Ltd., subcontracted the project to Bai Liuyun, a 60-year-old man who has been supervising bridge constructions in the city for many years.

Bai employed many farmers in the county for the project.

Realizing there was not enough earth around the site of the project, Bai decided to use wood structures to support the bridge, in stead of consolidating the groundwork with earth as stipulated in the contract, said Yang.

A downpour that had pelted the site for two days distorted the planks under the bridge, resulting in the collapse, said Yang.

Police have detained Bai and a work team comprising officials from the provincial, municipal and county governments are investigating the accident.

(Xinhua News Agency August 27, 2009)