A team of experts has been set up to test drinking water believed to have killed 700 chickens.

The intense publicity surrounding the "red water" has led to the resignation of the head of environmental protection and the company responsible for the pollution issuing a public apology.

"Experts have taken samples from ditches and underground water, including the water pumped from 50 and 100 meters deep," Tian Hongxia, a spokeswoman for Cangxian county, Hebei province, said on Sunday. "They need time to test all the samples."