At least 21 prisoners have died in a fight between inmates at a Mexican prison, officials said.

The Public Safety Department of Tamaulipas state said a pre-dawn clash between two groups of inmates at Reynosa prison on Monday also left 12 prisoners injured.

Relatives of inmates banged angrily on the prison doors demanding news of the welfare of their family members.

The cause of the riot and the inmates' deaths was under investigation. State authorities suspended the prison director and guards pending the investigation.

State and federal police, supported by army troops, took control of the state prison, located in the border city of Reynosa.

Soldiers and police also ringed the outside of the institution as relatives of inmates gathered.

Last month, two riots at La Mesa state prison in city of Tijuana, across the border from San Diego, California, killed at least 23 people, including two inmates from the US.

La Mesa prisoners argued that officials weren't giving them food and water, but prison officials blamed troublemakers for the violence.

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