An investigation has been launched into whether inmates at Goulburn jail have been trying to dig a tunnel after a hole was discovered in a workshop, the New South Wales Department of Corrective Services says.

The cavity, 60-centimetre deep with a 40 by 18 centimetre wide entrance, was found under a cabinet during a search of the furniture workshop at the jail in the southern tablelands.

The Department of Corrective Services said the cavity was more than 100 metres away from the outside wall of the prison.

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“It is not yet known who made the cavity or its intended use,” the department said in a statement.

The Government has promised to review practices and procedures at the jail following the discovery.

Corrections Minister David Elliot said he was satisfied with the way the matter had been handled.

“The cavity was found very quickly, the matter was dealt with very swiftly and I’m very confident at the way Corrections have responded to that,” he said.

“It could have taken a long time for anybody to escape, but the matter is an operational matter. I’ll be getting a debrief; we’ll make sure that any practices that need to be reviewed will be reviewed.”

Labor spokesman Guy Zangari said it was a sign that supervision levels had suffered because of budget cuts.

“A prisoner should not have been able to dig an inch or a centimetre and yet we find out that it’s 600 millimetres deep,” he said.

“I mean, that is just unacceptable. We simply cannot have inmates that are in workshops not being correctly supervised.

“This being found out today would indicate that the prison system is on its knees.”

The furniture workshop will remain closed to inmates until investigations have been finalised.

– ABC