Taliban spokesman Zabiullah Mujahid announced last week that tunnel used for the breakout at Sarposa Prison, just outside Kandahar, Afghanistan on 24 April benefited from expert consultancy.

Tunnel works began in a house to the southwest of the prison some five months ago and managed to emerge in the correct prison cell for the escape, said Mujahid.

The tunnel opening was 1m in diameter. From the cell it dropped immediately down 1.5m before running to the compound 360m away. According to Mujahid, muck disposal posed a particular problem, “We had proper digging equipment. There was so much earth from the tunnel that we carried it away gradually and sold it in the market.”

“The house where the tunnel was found was searched by security forces two-and-a-half months ago,” said Afghan justice minister Habibullah Ghaleb. “Earth or soil dug out of the tunnel must have been moved and should not have been missed.”

Around 470 of the 1,200 prisoners escaped during the operation. Three militants within the prison were aware of the plan, and woke prisoners a handful at a time to make their escape. Prison officials said they became aware of the tunnel at 4am, after the breakout.