Two prisoners were placed in the segregation block at Parkhurst Prison, Isle of Wight, after the discovery of a tunnel shaft at the top security jail.
The two were both Category A prisoners.
A Home Office statement said: ‘A prison officer, as a result of certain suspicions, called fellow officers and searched a workshop which is part of the recreational area.
‘Beneath the wooden floors they discovered a shaft four feet deep and the beginnings of a tunnel 34in long.
‘They also found a spade and home-made light fitting in the tunnel.’
A thin layer of rubble was stored in the space beneath the floor and the ground. It was thought work on the tunnel had taken two to three weeks.
It was assumed that the intention was to go under the wall and into the ground.
‘From the wall of the building it is 100 yards to the inner perimeter of the fence, which is patrolled regularly,’ said the spokesperson.
However they were not able to comment on how the men were able to start the tunnel shaft without being observed by Parkhurst’s prison officers.