JINAN -- Air pollutants were well below national alert lines after an explosion occurred at a pharmaceutical factory in East China's Jinan city Monday night, local government said.

After monitoring the levels of four major air pollutants near the factory, officials found the content of volatile organic compound and dichloromethane were under alert lines, while acetone and ethyl alcohol were not detected.

The blast happened at around 8:50 pm in a workshop for waste water reclamation in Qilu Pharmaceutical Company in Dongjia township, Licheng district.

Firefighters have rushed to the scene. No casualties were reported.

According to the official microblog of the city's public security bureau, smoke was spotted coming out from the east side of the factory.

A preliminary investigation found a pressure vessel with ethanol in it exploded in a workshop of about 400 square meters and released a little non-toxic gas, but did not cause open flames. There were no flammable or combustible materials nearby.

According to people living nearby, the explosion was felt strongly, and white powder and a burning smell filled the air.

Some residents said they were still worried about the air quality. The government said the environmental protection department is keeping track of the situation.

The factory has been suspended operation, and further investigation is under way.