BEIJING (AFP) - Nineteen people were injured in an explosion at a controversial chemical plant in the eastern Chinese city of Zhangzhou, the authorities said on Tuesday, the second accident at the site in two years.

Footage broadcast by China's CCTV News showed flames billowing into the air following the explosion at the plant producing paraxylene - a chemical commonly known as PX and used to make fabricin Fujian province.

The blast occurred on Monday evening and the 19 injured - including four firefighters - were being treated in hospital, the official Xinhua news agency reported, citing provincial authorities. It added that the fire was still not under control as of Tuesday morning.

Some 829 firefighters battled the blaze, Xinhua said, adding that witnesses reported feeling a tremor as far as 50km away.

Local residents had been evacuated, it added, and the fire had been contained. It was caused by an oil leak at the facility which then caught fire and set off explosions at three nearby oil tanks, the report said.

It is the second accident in 20 months to occur at the facility, Xinhua reported.

Proposals for plants producing PX, a flammable, carcinogenic liquid used in the production of polyester films and fabrics, have sparked large protests in several Chinese cities in recent years over perceived health risks.

The Zhangzhou PX plant was originally slated to be built in the nearby coastal city of Xiamen, but was moved to its present site after thousands took part in a protest in 2007.

In March last year thousands of demonstrators also took to the streets of Maoming, in the southern province of Guangdong, for days of demonstrations against another PX plant.

The rallies underscored the increasing number of angry protests over environmental concerns in the country, where three decades of rapid and unfettered industrial expansion have taken a heavy toll.

China's environmental minister in March said that construction of PX projects must be "scientifically decided and must pass environmental impact assessment", Xinhua reported Monday.

In a sign of the ruling Communist Party's sensitivity to the debate over environmental issues, comments had been disabled on a report on the Zhangzhou incident on the Netease web portal as of Tuesday morning.

Yet discussion of the explosion dominated China's popular online social networks, with many users citing the incident as vindication of environmental protesters' fears.

"Do you remember what we were worried about at the time?" wrote a user on Sina Weibo, a Chinese Twitter equivalent, referring to similar protests in the north-eastern city of Dalian in 2011.

"What we worried about is now the reality in Zhangzhou."

One user wrote: "Only when the city officials and their families live near a PX plant will their assurances be convincing."

Another opined: "They should build a PX plant in Beijing."