An explosion at a fireworks factory in north-eastern Spain has killed at least two people, wounded six and left four others missing.

The blast occurred around 2pm local time at the Pirotecnia Zaragozana factory in the small town of Pinseque, a police spokeswoman said.

The wounded were taken to a hospital in the nearby regional capital of Zaragoza.

Police and firefighters were searching the area for the missing people, she added.

Spanish national television said continuing blasts in the aftermath of the main explosion were hindering the search operation.

The blast sent a dense plume of white smoke into the sky that could be seen for miles.