Plan by thieves who hoped to steal up to £250 million in what would have been world’s biggest bank robbery this weekend, was foiled by Police in Sao Paulo after discovering a 500-metre tunnel, complete with lighting, ventilation and rail tracks, leading from a rented house to the vaults of the Bank of Brazil.

Several bullet-proof cars, suspected of having been prepared as getaway vehicles, have been impounded as part of the police operation.

“It would have been the world’s biggest heist,” said Fabio Pinheiro Lopes, the police chief of Brazil’s financial capital.

“They are an extremely dangerous and organized gang with a long history, including some violent crimes like homicide. If you look at their ages most are above thirty five – well above the age of your average Brazilian criminal,” he added.

Sixteen suspects were arrested at a warehouse on Monday night in the northern suburbs of the city, where the gang stored tools to dig the tunnel and tracks to remove the money.

Altogether, police say 20 members of the gang invested 200k Brazlian reais each – a total of 4m reais for the robbery. Police monitored the group for at more than two months.

The tunnel, which allegedly took four months to build, was illuminated and ventilated and supported by wood and iron.

Police are looking for a woman that rented the house for the gang using false identity.

The gang reportedly invested £750,000 to fund the construction of the tunnel and other logistics.

Police allege the leader of the gang was Alceu Ceu Gomes Nogueira, a 35-year-old man implicated in an attempted robbery of a security van in Paraguay.

The court ruled the group be held in pre-trial detention.

The group dug the tunnel by hand, loading the soil into sacks and carrying it through a fork in the tunnel to an underground storm water drain.

To enter the tunnel, gang members descended a two meter ladder from one of the rooms in the rented house. The tunnel was about 1.5 meters high and was reinforced with iron beams and wood, and was even wired with lights.

The walls were lined with plastic garbage bags to reduce the dust. The house was reportedly filled with food, water, special clothing and digging tools.

Police were probing whether the gang had the assistance of a engineer when building the tunnel. The tunnel renewed memories of a tunnel robbery 12 years ago when thieves made off with about US$ 70 million.

On that tunnel, diggers worked in shifts from 8 p.m. until 4 a.m., taking a break on weekends. Three gang members involved in that attempt were involved in two separate prison escapes using tunnels equipped with ventilation and lighting.