Four people have been killed and 21 others injured after a truck loaded with fireworks collided with another vehicle and exploded in east China's Anhui province, local authorities announced Wednesday.

The accident happened at about 5 p.m. Tuesday on an expressway linking Anhui and Hubei provinces, according to the publicity department of Lujiang county, where the crash took place.

Fireworks on the truck were set off in the collision, killing the drivers of both vehicles and two passengers on the spot, sources said.

The blast also injured 21 villagers nearby, with four in serious conditions. The injured were instantly sent to hospitals.

Firefighters said the blast also toppled several houses and shattered the windows of dozens of homes.

Police are further investigating the cause of the accident.