Two major water suppliers in a central China city have halted production following water contamination in a local river on Wednesday, affecting more than 300,000 people, local authorities said.

The Baihezui and Yushidun water plants in Wuhan, capital of Hubei, suspended water production at around 4 p.m. and 7 p.m. respectively, after tests showed that the Wuhan section of the Han River, a major tributary of the Yangtze River, contained excessive amount of ammonia and nitrogen, the city government said in a statement.

Their moratorium of water supplies has caused a water shortage in an area of 260 square km in the city, affecting hundreds of food manufacturers as well as the livelihood of local people, according to the statement.

As of 9 p.m., water supplies in the city had been up to standard, the statement said. Local departments are testing the river water every hour, while environmental protection bureaus on the provincial and city levels are investigating the source of the pollution, it added.