At least nine people died and 11 others were injured after a truck loaded with fireworks exploded and caused part of a highway bridge to collapse in Central China's Henan province.

The explosion occurred at about 8:52 am Friday when a truck carrying fireworks was on a 30-meter-high bridge in Mianchi county of Sanmenxia city, said Ren Zhanzhou, deputy director of the city's publicity department.

Rescue workers conduct rescue work after an accident that killed five people and injured eight others when an expressway bridge partially collapsed due to a truck explosion, Feb 1, 2013, in Central China's Henan province. [Photo/CFP]

At least 25 vehicles fell to the ground after an 80-meter section of the bridge collapsed, Ren said.

None of the vehicles were loaded with dangerous chemicals, he added.

Seven people died at the scene and two others died on the way to hospital. At least four of the 11 injured people are in serious condition, according to Xinhua News Agency.

Li Mengliang, a villager whose house is 500 meters from the collapsed bridge, said he was eating breakfast with his family when the explosion occurred and the loud noise shocked his family.

"It was like an earthquake," he said.

There was a strong odor of gunpowder in the air after the accident, Li said.

Zhong Yongliang, a local villager, said the windows in his home were shattered by the shock wave from the explosion.

The highway, with a total distance of 4,395 km, links the coastal city of Lianyungang in East China's Jiangsu province and Horgos, a border port in Northwest China's Xinjiang Uygur autonomous region.

The highway was sealed off in both directions after the accident, and many vehicles had to travel on other highways, said Liu Xiaoting, deputy Party chief of Mianchi county.

"It caused a serious traffic jam, since it's the travel peak ahead of Spring Festival and many people are rushing home," he said.

Fireworks quality

The fatal accident has raised public concern over the quality of fireworks production and the safety of fireworks transportation.

The Ministry of Public Security vowed to enhance supervision of work safety in fireworks production.

Those who produce fireworks of substandard quality must be punished, according to the ministry.

Huang Ming, vice-minister of public security, went to Henan province on Friday afternoon to investigate the accident, the ministry said.

An official from the General Administration of Quality Supervision, Inspection and Quarantine, who preferred to remain anonymous, said investigations are needed to decide whether the accident was caused by substandard fireworks.

About 17 percent of the fireworks and firecrackers being sold ahead of Lunar New Year fail to meet quality standards, according to the administration.

The administration recently sampled 300 batches of fireworks made by 201 companies in 10 provinces and autonomous regions, and about 50 batches made by 43 companies failed to meet quality standards, it said at a news conference on Jan 28.

Problems with fuses, labels and body thickness were found in the substandard products, it said.

Fireworks and firecrackers are hot sellers during the holidays around China's Spring Festival, which falls on Feb 10 this year.

China is the world's largest producer of fireworks and firecrackers, accounting for 90 percent of the world's total production, Xinhua reported.

The administration urged consumers to buy fireworks and firecrackers from certified stores to avoid substandard products, and to set them off in safe places.

"Improper operation of fireworks or firecrackers or handling substandard products is very likely to result in major accidents," it alerted.

Zhang Guowei, head of the Henan Department of Work Safety, said that the provincial government is going to check the work safety of fireworks production.

Ma Shouguo and Zhang Leilong contributed to this story.