A Chinese man has been arrested for allegedly poisoning a reservoir to boost his sales for water purifiers.
Cao Qian, 27, tossed 500 millilitres (about a pint) of pesticide into a reservoir in central Henan province, China's Xinhua news agency reported.
No deaths were reported, but 64 people were sickened and 42 of them sent to hospital, Xinhua said.
Mass poisonings are not infrequent in China - either as a result of poor hygiene, or as a means of vendetta.
Mr Cao, an unemployed man, was trying to run a small shop selling water purifying devices, Xinhua said.
More than 9,000 families were reported to have been affected by the water in Ruyang county, which was poisoned on Wednesday, according to the agency.
Last month, dozens of people at an elementary school in central China were taken to hospital after ingesting rat poison with their school breakfasts. Authorities said the poisoning appeared to be deliberate.
And last year, at least 38 people died in the eastern city of Nanjing after
eating snacks that a rival shop owner had laced with poison.