Four workers are reportedly missing and four others seriously injured after a dam collapsed in Cambodia, officials said Sunday.

A portion of the hydroelectric dam gave under the weight of the amount of water and began leaking, Maj. Theang Leng, chief of police in the district, told AP. Search operations are under way for the missing workers who were believed to have drowned while construction work was halted as authorities survey the damage.

China Datang Corp. began constructing the $255 million-worth 120-megawatt Atay hydroelectric dam in 2008 and is expected to be finished by May 2013. The company is set to operate the project for 30 years under a build-operate-transfer concession, AP reports.

The construction of hydroelectric dams came under criticism because of the environmental and social impact they have amid Cambodia’s electricity shortage.

US-based watchdog group International Rivers Networks said in its 2008 report that “poorly conceived hydropower development could irreparably damage” Cambodia’s environment and social costs. Villagers are being displaced and deprived of the natural resources.