The picture shows heavy smoke rising to the sky when a blaze broke out at a plastic packaging factory on Thursday, July 17, 2008 in Shanghai. [Photo: chinanews.com]

An overhead beam crushed three firefighters to death and injured nine others as they fought a fire at a plastic packaging factory on Thursday in Shanghai.

Structural flaws in the storehouses are blamed for the accident, police said.

The blaze broke out at around 12:20 p.m. in the storehouses of Rexam Plastic Packaging (Shanghai) Co. Ltd. in Fengxian District, according to the municipal firefighting and work safety departments.

At 2:05 p.m., a major support beam, 50 meters long, suddenly fell and crushed many firefighters. Three died at the scene, while nine others were injured.

The three dead firefighters -- Yao Lei, 20, Shi Jianhua, 31, and Yu Hai, 27 -- were all from the Fengxian firefighting detachment. They were all praised by the city authorities.

More than 300 firefighters had contained the fire around 6 p.m. and extinguished the remaining flames by 8:00 p.m.. The fire spread to 2,000 square meters.

The injured firefighters were being treated in hospitals and were not in any danger, doctors said.

No one at the factory got hurt.

Residents within 200 meters of the plant in southwest Shanghai had been evacuated.

The city's environment authority were also at the site to monitor the air quality as the smoke from the burning plastic materials could be harmful.

They found that the content of styrene was slightly higher than usual in the atmosphere within a square kilometer. The air quality outside that area was barely affected by the accident.

The municipal environment authority said southeast winds, measuring force 3-4, blew in Shanghai on Thursday. Fengxian District, where the accident occurred, is in the southwest of the city, so the smoke and dust were unlikely to flow to the downtown area.

British firm Rexam is one of the world's largest consumer packaging groups and a leading beverage can maker. Its Shanghai company was established in 1992.