About 40 southern separatists escaped from a prison in Yemen after a guard lobbed a hand grenade to disperse an inmates’ protest at the facility, officials said on Thursday.

The men escaped amid a melee that erupted when the grenade exploded in the prison in the southern town of Dali, the officials said. Authorities immediately imposed a curfew on the town and launched a manhunt to track down the escaped inmates.

The officials, who spoke on condition of anonymity because they were not allowed to speak to the media, said four prisoners were wounded in the blast. The inmates were protesting their detention without trial.

Southerners in Yemen complain of neglect and discrimination by the north, and an increasingly vocal southern separatist movement has been coming to blows with the central government. The two parts of the country were separate nations before they united in 1990.

Also on Thursday, police fired tear gas to disperse protesters in Dali and several other southern towns. The demonstrators were protesting the government’s ongoing crackdown against southern pro—secession activists.

Police officials said scores of protesters were detained.

Tensions have recently escalated in the south, adding to the challenge Yemen’s government already faces from an al—Qaeda movement that has set up operations there and a northern rebellion.

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