At least one person died and 40 were injured in an explosion at a candy factory in Mexico.

The blast inside the Dulces Blueberry factory in Ciudad Juarez triggered a fire that tore through the building and caused the roof to collapse.

"I was able to help five people who walked out of the building but as soon as they were out they went into shock and fainted," said factory worker Ismael Bouchet.

The explosion occurred on the second floor of the factory, which produces gummy bears, jelly beans, peach rings and other sweets. Authorities believe it was caused by a recently installed boiler.

"Since the morning, several co-workers said there was a bad smell, that it smelled of acid and because it was a new area we thought it was normal," Bouchet said.

Photos of the incident showed some of the workers sporting injuries that resembled chemical burns.

Some 300 people were believed to be in the building when the ceiling caved in.

Ciudad Juarez Civil Protection Director Fernando Mota said several people are still missing and might be trapped inside.

Eleven of the injured have been taken to hospital in a serious condition, authorities said.

Ciudad Juarez Candy Factory explosion
At least 40 people were injured in the blast and fire Reuters
Mexico Factory fire
Paramedics attend to an injured person as employees leave the Dulces Blueberry candy factory after the blast Reuters
Mexico factory expolsion
Some of the workers at the candy factory in Ciudad Juarez sported injuries that resembled chemical burns Reuters
Dulces Blueberry explosion
Debris lies outside Dulces Blueberry candy factory after the explosion Reuters
Mexico Candy Factory Blast
Police officers walk outside a candy factory after an explosion in Ciudad Juarez Reuters
Mexico Candy Factory Fire
An injured person is seen outside the candy factory Reuters
Ciudad Juarez Factory blaze
Paramedics move an injured person to an ambulance outside the candy factory in Ciudad Juarez Reuters
Mexico