A third arrest has been made in connection with explosive substances being found near the 2012 Olympic stadium in Stratford.

Police have revealed that at 6.25pm this evening officers from the Olympic Site Support Unit arrested a 61-year-old man on suspicion of supplying an explosive substance.

He was arrested on the Olympic Park site. He has been taken to an east London police station.

A spokesman said: “The arrest is part of an ongoing investigation that started on March 29 following the arrest of a 40 year old woman on suspicion of possession of an explosive substance.”

The female security guard arrested near the Olympic stadium on suspicion of possessing explosives has been released on police bail.

The woman, a dog handler with private security firm G4S, was detained after her vehicle was searched in a car park off Pudding Mill Lane, Stratford.

She was questioned at an east London police station and has been bailed to return later this month. A 43-year-old man from Wales has also been arrested in connection with the explosive find and has also been bailed.

Scotland Yard said the arrests were made by the Olympic Site Support Unit (OSSU) following a tip-off and that site safety had not been at risk.

It is understood they were part of an ongoing investigation and are not terrorist-related. Searches were also carried out at residential addresses in Kent and London.

It is understood a very small amount of a substance recovered by police was forensically examined. The arrests came on the day building work was completed at the �486m Olympic Stadium.

A spokesman for the Olympic Delivery Authority said: “There are robust measures to ensure the safety and security of the Olympic Park.

“We are working with the police in their investigation. At no point has the safety and security of the Olympic Park been put at risk.”

Bosses at G4S said they would be assisting police with their inquiries.