JINAN, Jan. 2 -- A toxic gas leak in east China's Shandong Province killed four people and injured three others as of 8 a.m. Thursday, local authorities said.

The gas leakage happened at a chemical company in the economic development zone of Yangxin County, Shandong at about 11:20 p.m. Wednesday.

An initial investigation showed that leakage took place in a flange connecting naphtha storage tanks.

The case is under further investigation.