A strange odor on Thursday morning in the central urban area of Wutongqiao district in Leshan, Sichuan province — identified by netizens as chlorine — caused residents to flee.

The district government said in an online post that investigators were trying to determine the cause. So far they had found no leaks at any local chemical enterprise.

Zhang Guoqing, the district's Party secretary, and other leading officials rushed to the scene and found nothing abnormal, the post said.

Departments in charge of the environment are monitoring the situation. No excess chlorine or other gases have been found in the area, it said.

Water and gas sampling and testing were being carried out, with results expected to be announced in a timely manner, it added.

A local pesticide company said in a statement that when the recent flood receded on Wednesday, the company began giving itself a thorough cleaning and found all its equipment and devices in normal condition.