Troubled HMP Birmingham has been placed in temporary lockdown, the Ministry of Justice (MoJ) has confirmed.
Inmates have been confined to their cells during a “pre-planned, intelligence-led search”.
A former prison officer, who did not wish to be named, said he understood all cells were being checked and contraband confiscated.
The government took over from security service G4S last summer over the prison’s “appalling” conditions.
It is understood the search has been going on at least two days but the MoJ would not confirm when it started or how long it would last.
It did however reveal it is not in response to any particular incident.
“HMP Birmingham has been temporarily placed in lockdown to assist with a pre-planned intelligence-led search of the facility,” a spokesman said.
“The search is one part of our long-term safety and security strategy to improve conditions at the prison.”
The prison was the scene of a riot in 2016 and subsequent damning inspection reports lead to it being taken out of the control of G4S in August.
Extra officers have since been brought in and inmate numbers reduced under a new governor and monitors said in November it was now “turning a corner”.
However, earlier this month, Prisons Minister Rory Stewart said the takeover would be extended for six months as it remains in a “fragile state”.
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