The Shanxi provincial government said it received a report regarding the leak on Saturday, adding that an emergency response had been initiated to stop the leak and clean up the pollutants.
Another 30 tonnes of spilled aniline have been contained in a nearby disused reservoir, the local emergency response headquarters said.
A statement from the municipal government of Changzhi, which administers Lucheng, said the leak has not resulted in any casualties so far, adding that the river's water quality has been recovering.
Concentrations of aniline in the river have decreased to 2.15 mg per liter from the previous level of 72 mg per liter, according to data from a monitoring station on the river.
However, the concentration should be less than 0.1 mg per liter, according to national standards.
Girl wearing "military uniform" parade on the street to publicize the new traffic regulation