The explosions and fires at a petrochemical plant in Nanjing, Jiangsu province, which lasted from Monday to Tuesday, have not caused air or water pollution in the neighboring area, according to the local environmental protection bureau.

Around 1 pm on Monday, a tank of the sulfur recycling unit containing acidic water at the Sinopec Yangzi Petrochemical Company Ltd exploded and caught fire. The blaze later ignited a nearby waste oil tank and two other tanks holding acidic water used to produce sulfur. Each of the tanks had a capacity of 2,000 cubic meters.

Although the fire was extinguished three hours later, the tanks, which burned to the ground, ignited again at 6 pm.

More than 200 firefighters from across the city rushed to the plant to help extinguish the fire. No one was injured by the explosions or fires.

"The oil floating on the acidic water produced a large amount of smoke due to incomplete combustion," said Zhou Wenhu, head of the plant's fire department. "The petrochemical smoke has a pungent smell and may cause discomfort."

"Neither the provincial nor the city's environmental protection departments asked us to evacuate the surrounding area," Zhou said.

According to Nanjing's environmental protection bureau, no hydrogen sulfide was detected by the three monitoring stations that are located 1 kilometer away from the plant in readings taken after the fire started and two hours later.

It also said that the water used to extinguish the fires was mostly kept inside the plant by closing the plant's sewage discharge valves, thus preventing any influence on the neighboring environment.

"The Yangzi company apologizes to the Nanjing residents for the accident," said Sun Ping, spokesman for the petrochemical company. "A team has been formed by the company and Nanjing's fire and public security departments to investigate the fire. We will release information to the public in time."

Yangzi Petrochemical Co, which operates more than 60 sets of large-scale petrochemical units, is one of China's biggest suppliers of pure benzene, paraxylene and some other chemical products, according to its official website.

It is capable of processing 9 million tons of crude oil, 650,000 tons of ethylene and 1.4 million tons of aromatic hydrocarbons a year, with annual sales revenue reaching nearly 60 billion yuan ($9.6 billion).