A major city in western China is in a panic after government officials said the tap water in the city is toxic.

Government officials in Lanzhou say that excessive levels of benzene have been found in the water system.  The amount of benzene is reportedly 20 times the acceptable limit to not be a toxic threat to someone who consumes it.

Benzene has been linked to leukemia and non-Hodgkin’s lymphoma.

“Consuming foods or fluids contaminated with high levels of benzene can cause vomiting, stomach irritation, dizziness, sleepiness, convulsions, and rapid heart rate. In extreme cases, inhaling or swallowing very high levels of benzene can be deadly,” the American Cancer Society said.

Lanzhou is a city of 2.5 million people and witnesses report panicked residents flooding into stores to stock up on bottled water.

Chinese officials would not name a source for the toxic levels of the chemical in the water but a source inside the government told the Daily Telegraph that there was a spill from an unnamed chemical plant.

A 2012 study found that 60 percent of the groundwater in China is “heavily polluted.”