Three suspected fraudsters were arrested following an incident at the tunnels on Thursday, August 28.
At 9.20pm that day, a black BMW was heading northbound through the Tyne Tunnels when they asked the barrier supervisor to pay on card.
The customer was handed the card machine and it was passed around the car – but it is suspected a refund card was used to take £36,000 from the tunnel's accounts.
Sea fret - a look at the foggy phenomenon which spoils sunny days in South Shields
South Shields man jailed for terrifying physical and sexual assault on woman in her own home
South Tyneside man given jail warning after breaching court order
13 great pictures as the sunshine sees crowds flock to South Shields beaches
The 16 places where most crime was reported across South Tyneside in June
When it appeared that those in the car had paid the toll, they handed the card machine back to staff before carrying on with their journey.
But the behaviour of the men in the vehicle left staff suspicious, prompting them to contact the fraud team, who then discovered a £36,000 payment had been taken.
The payment was cancelled and Northumbria Police were called – with officers able to hold the vehicle at the barrier after it turned around and drove through the tunnel in the opposite direction.
Three men, aged 25, 25 and 24, remain in custody as inquiries into the suspected fraud continue.
Detectives have praised staff at the tunnel for their vigilance and said they could have prevented a "serious and sophisticated scam".
Detective Constable Thomas Stockport, of Northumbria Police's Northern CID, said: "This was a fantastic example of partners working together to take quick action against those suspected to be involved in criminality.
"From what we know this is a serious and sophisticated scam that could have resulted in these men getting away with tens of thousands of pounds.
"None of the three men are from the area and when they were arrested we found a number of credit cards, mobile phones and a number of receipts.
"But these arrests would not have been possible if it were not for the quick thinking of staff at the Tyne Tunnels and their colleagues in the fraud team.
"I want to thank the staff who intervened, and the responding police officers, for helping us to bring these men into custody."
Phil Smith, CEO of TT2 Limited, added: “We would like to give credit to the senior tunnel officer on the plaza at the time of this alleged incident, who identified the suspicious activity and reported it to our fraud team, who acted quickly to ensure no money was taken.
“We’d also like to thank the team at Northumbria Police, with whom we have a positive working relationship, for their quick response to apprehend the individuals when they came back to the tunnel for their return journey.
"It was a demonstration of excellent teamwork, which I hope will deter others from attempting similar crimes in the future.”