Nitric acid that spilled from a crashed truck in a northwest Chinese city Monday has caused no contamination of the Yellow River -- China's second longest river, local officials said.

Workers had cleaned up tons of acid that entered a roadside drain in a four-hour operation after the accident in Lanzhou, Gansu Province, said a spokesman of a work crew tasked to clean up the chemical.

Tests show the spill did not pollute the environment near the Yellow River, he said.

Officials with the city environmental protection bureau said they would keep monitoring the water quality of the Yellow River.

A truck carrying 14 tonnes of nitric acid overturned and caught fire on Liuzhong Highway near Lanzhou at noon on Monday. One driver was killed while the other was seriously injured.