Lanzhou city in northwest China's Gansu province canceled emergency water supply to Anning district at 5 p.m. Sunday, as the contaminated tap water was found safe there, local government said.

Crude oil leak from a petrochemical pipeline poisoned the water source for a local water plant and brought hazardous levels of benzene into the city's tap water on Friday morning, affecting 2.4 million people.

In Anning district, the benzene levels were tested between 7.86 micrograms and 1.12 micrograms per liter of water for eight samples since 1 a.m. Sunday. China's national limit for benzene in tap water is 10 micrograms per liter.

On Saturday, local government stopped emergency supply of free drinking water to the districts of Chengguan and Qilihe after the environmental monitoring department found no excessive benzene in four tests of samples taken from two downtown surveillance sites of the two districts.

According to Zheng Zhiqiang, deputy head of the investigation team of the incident, the underground poisoned water from the water source will be further tested to confirm the connection between the oil leak and the contaminated tap water.

The tap water contamination caused panic on Friday. Stores and supermarkets ran out of bottled water, and many people complained of thirst.

Fire engines and water sprinklers carried water to downtown communities for emergency supplies, and residents fetched water with pots, basins and buckets until after midnight.

From Thursday evening to early Friday morning, Veolia Water, a Sino-French joint venture and the sole water supplier for urban Lanzhou, found between 118 micrograms and 200 micrograms of benzene per liter of water at their plants.

Benzene is a colorless carcinogenic compound used to manufacture plastics. Benzene is known to damage the human hematopoietic system, which produces blood.