The tunnel started from a toilet in the prison [Photo: Courtesy]

A prisoner who was just metres from escaping after digging a 70 metre long tunnel from his cell toilet suffocated to death, it was reported today.

Judson Cunha Evangelista, 26, is believed to have suffered from lack of oxygen as he carved the tunnel, which had already passed under perimeter wall of the maximum security jail in Boa Vista, northern Brazil.

The tunnel is understood to have taken months to excavate and was reportedly just a few metres away from reaching the surface in surrounding forest outside.

It is thought the prisoner was planning to charge other inmates to use the tunnel in a mass escape bid.

The escape route was discovered by police today who are investigating whether the inmate, who was serving time for murder, made it back to his cell after becoming ill inside the hole.

Shocked officers discovered the hole which began underneath the toilet in Evangelista’s cell in the Monte Cristo penitentiary, the largest prison in Roraima, north Brazil.

The dirt tunnel continued for 70 metres underneath the prison and had already passed under its heavily-fortified outer walls and electric fences, according to prison authorities.

Officers found several bags of dirt and an electric cable which ran the length of the tunnel, with a lightbulb on the end.

The state justice department, Sejuc, which is in charge of the prison, said 150 policemen took seven hours to locate the tunnel after prison officers were alerted to its existence following Evangelista’s death.

The tunnel has now been filled with concrete, a spokesman said.

Last January the Monte Cristo jail made headlines after a bloody rebellion broke out during which more than 30 prisoners were killed.

At the time the prison, which has capacity for 750 inmates, was housing more than 1,400.