HOHHOT: Altogether 1,154 people have sought medication for gastrointestinal illness after the town's tap water supply was contaminated by rainfall Saturday in Chifeng City of north China's Inner Mongolia Autonomous Region, the local health authority said Tuesday.

As of Monday night, 15 people were hospitalized and medicine was prescribed to another 110 people, a spokesman with the city's health department said.

He said all the other patients had mild cases and their symptoms has subsided by the time they visited the hospital.

The patients complained of fever, diarrhea and vomiting after drinking tap water at home Saturday and Sunday, he said, adding that they were from eight downtown communities in Chifeng.

The local government has vowed free medication for all the victims.

On Monday, a government official blamed the pollution on heavy rainfall of July 23, saying it raised the city's water level and caused water from a nearby lake to flow into the water supply system.

The local health authority is conducting lab tests of the water.

Residents in Chifeng are buying bottled water amid the pollution scare.