A truck transporting fireworks in the runup to Chinese new year celebrations has exploded on a highway in central China

A truck carrying fireworks in central China exploded on Friday morning, destroying an expressway bridge and killing at least six people, according to state media reports.

The explosion occurred amid heavy fog on the Yihang bridge near the city of Sanmenxia in central Henan province at about 8.52am, according to the state newswire Xinhua, causing an 80-metre section of the bridge to collapse and sending six vehicles plummeting 30 metres to the ground.

Xinhua initially reported that there were four deaths, but the number rose to five in the early afternoon and again to six when another corpse was pulled from the wreckage at 3.30pm. An earlier report by China National Radio, also state-run, put the death toll at 26, but the report has since been retracted. 11 injured people were rushed to two nearby hospitals, three of whom have died.

The force from the explosion threw six cars into a ravine beneath the bridge and shattered windows at nearby service stations, according to the People's Daily website. The south side of the bridge collapsed completely and the north side is still unstable, it said.

The People's Daily quoted experts as saying that the force of a firecracker explosion could in fact destroy a bridge, underscoring widespread concerns in China about the quality of the country's rapidly constructed infrastructure.

Six vehicles have so far been retrieved from the debris and emergency workers have closed off the highway near the accident, according Xinhua. Search and rescue efforts are ongoing.

Pictures posted online show a highway strewn with rubble, a red truck stopped dangerously close to the edge of the broken highway, and a pile of wrecked vehicles in the ravine far below.

The accident is a stark reminder of safety hazards often associated with Chinese new year celebrations, which begin this year on 10 February. 5,945 fire accidents were reported during the first day of last year's spring festival alone, according to Xinhua.

In 2006, 367 people were killed at a temple fair in Henan when a storeroom of fireworks exploded, according to the Associated Press. Six years earlier, an explosion at an unlicensed fireworks factory killed 33 people, many of them children.

The Chinese government outlawed fireworks from 1993 to 2005, but ultimately lifted the ban under intense public pressure.