Medical personnel in Fuquan, Southwest China’s Guizhou province, carry a man who was injured during a blast that killed at least seven on Tuesday. PROVIDED TO CHINA DAILY

FUQUAN, Guizhou - Two trucks, fully loaded with explosives, set off a big blast near a small town in Southwest China's Guizhou province on Tuesday, killing seven people and injuring 264, local authorities said.

The explosion occurred at 11:30 am when the trucks carrying 70 tons of explosives were being repaired in a factory in Machangping township of Fuquan city, local authorities said in a statement.

As of late on Tuesday, seven people had been killed in the blast, Huang Kangsheng, vice-governor of Guizhou, who arrived in Fuquan earlier, said on Tuesday evening.

A total of 264 injured people, including 25 in serious condition, were rushed to hospitals, said Huang.

"It felt like an atomic bomb detonating near me," said Gao Shu from Liaoning province, who was driving past when the trucks exploded.

Gao said his car was about 500 meters away from the trucks.

"Numerous pieces of stones were falling from the sky," he added. "The shock wave knocked the car out of control even though I stamped on the brake."

Gao was not injured, but four others traveling with him were wounded by the blast. One of them suffered severe injuries in the eyes, he added.

On Tuesday evening, rescuers wound up operations to search for survivors and retrieve dead bodies.

Preliminary investigation found that at least one man was killed at the repair factory. The trucks, which were heading for Guiyang, the provincial capital, from the neighboring Hunan province, had been so completely shattered that the debris was untraceable.

The identities of the deceased are yet to be confirmed, according to Huang.

Almost all of the injuries were caused by broken glass, he said, adding that the local government will pay for the medical expenses.

Local authorities had mobilized 29 ambulances to rush the injured to hospitals in the cities of Fuquan and Guiyang.

The blast caused widespread damages in the town, leaving two deep craters at its epicenter. It ripped through a tollgate about 20 meters away from the explosion site, and shattered all the windows of buildings located within a radius of 3 kilometers.

Two granaries located nearby, holding about 8,600 tons of stock, were so damaged that the grains burst out, shattering the iron doors.

The blast also caused an outage in the town. The local power company was struggling to restore power supply on Tuesday evening.

Huang estimated that more than 20,000 residents in the town had been affected by the blast - their homes damaged to different degrees.

Local authorities have launched investigation into the cause of the accident.