Bosses at security firm G4S, which runs HMP Oakwood in South Staffordshire, have put contingency plans in force as a rooftop protest continues at the prison.
A spokesman confirmed six prisoners were involved in the incident.
We can confirm that an incident involving six prisoners is taking place at HMP Oakwood.
The Ministry of Justice has been alerted and our normal contingency plans have been enacted.
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Protesters gathered outside the Library of Birmingham following the announcement the £189 million building will now be closed on Sundays