Brazil police foil tunnel crew's plot to pull off 'biggest bank robbery in history'

A gang of industrious and audacious robbers was arrested on Tuesday after digging a 500m long tunnel to try and steal $405m from a bank vault in Sao Paulo.

Detectives were jubilant after thwarting what local media reported what would have been "the biggest bank robbery in history".

Raids in Sao Paulo ended with 16 people arrested after police had secretly monitored the crew's mammoth tunnel excavation.

The thieves had worked for four months on their underground passage, which began under a rented house and was designed to exit inside a main vault rammed with cash in Bank of Brazil.

Photographs taken inside the tunnel showed a trail of lights pinned to the low ceiling, and the walls and roof supported with iron bars and wood.

A lead detective said the gang had spent $1.6m building the tunnel.

"It would be the biggest assault in the world," investigator Fábio Pinheiro Lopes said on Monday.

Some of the gang are known to police, and had been involved in several other high profile heists.