At least four people have been killed in an early morning explosion in a chemical plant in Guangxi Zhuang Autonomous Region. [Hechi Daily]

Rescuers said that at least four people were killed, 44 others were injured and 17 were missing after a chemical plant explosion in south China's Guangxi Zhuang Autonomous Region early on Tuesday.

It wasn't immediately known how many people were in the plant at the time of the initial blast, at about 6 a.m., and the cause hasn't yet been established.

More than 10,000 people living within 3 km of the plant, owned by Guangxi Guangwei Chemical Co., were evacuated after the explosion, the rescue headquarters said.

Witnesses said they saw thick smoke envelop the plant, and the fire was so extensive that it hampered access.

Ma Dewen, chief of the Guangxi Zhuang Autonomous Regional Firefighters General Squad, rushed to the scene to direct rescue efforts as hundreds of firefighters from neighboring cities were called out to fight the blaze.

The explosions persisted until almost 1:00 p.m. and the fire spread over 10,000 sq m, said an unidentified firefighter who participated in the rescue operation.

"With explosions continuing and a fire raging, it is quite treacherous for rescuers, since there are huge hidden dangers amid the blasts, along with leaks of toxic gases such as ammonia and formaldehyde," said the firefighter.

The plant mainly produces polyvinyl acetate (PVA, used in adhesives) calcium carbide, and vinyl acetate monomer (VAM, used in paints, adhesives and coatings).

The plant is in a development zone of Yizhou City, a four-hour car drive from the regional capital of Nanning.

The plant has assets of 340 million yuan (50 million U.S. dollars) and produces about 300 million yuan a year in chemical products. Its largest shareholders are state-owned companies.