An explosion at a fireworks market outside Mexico City has killed at least 26 people, officials say.

Dozens of other people were injured as the blast hit the San Pablito fireworks market, about 20 miles (32km) outside the city.

Video from the scene showed a large number of fireworks rocketing into the air as they caught fire.

Dozens of paramedics and police attended the scene. The cause of the explosions is not yet known.

Locals have been told to avoid the area and keep roads clear.

State governor Eruviel Avila said the top priority was to care for the injured, and officials had been dispatched to the scene.

Fireworks continued to explode after the initial blast, as smoke billowed from the area in thick black clouds.

Photos from police and medical personnel at the scene showed several injured people among the destroyed market stalls, with brick buildings scorched by the heat.

"The sound of blasts started to go off and we thought it was a nearby fireworks workshop," local resident Alejandra Pretel told the AFP news agency.

However, she said it soon became clear the entire market was at risk.

"My neighbours said they felt everything shake, but I didn't realise because I was running away," she said.

The president of Mexico, Enrique Pena Nieto, tweeted condolences to the families of those who lost their lives, and wished a speedy recovery to the injured.

He also said members of the defence forces were assisting in the emergency.

The San Pablito market was heavily damaged by similar fires in September 2005, when a chain of explosions just before the country's independence day celebrations injured dozens of people.