Roughly 1,500 tools were seized by Metropolitan Police officers at Warren Farm Bonzer Boot Sale on May 1.
A search of a property in Hackney saw another 159 tools recovered.
Items recovered included three surveillance systems used to monitor earth and infrastructure movements, each worth more than £30,000.
A ground depth measuring device worth £20,000 and a motorised heist understood to fetch £17,000 were also seized.
Four men and two women, aged between 25 and 60 and from Hackney, Newham and Kent, were arrested on suspicion of handling stolen goods.
They have since been bailed while officers carry out further enquiries.
Cllr Ray Morgon, Leader of Havering Council, added: “This is once again excellent work from our trading standards team working in partnership with police and other partners.
“Illegal and harmful products have been taken off the streets in our borough as a result of this operation. I know there has been a lot of work to get this result, so I thank everyone involved.
“It’s our aim to help keep our residents safe and we want to continue to crackdown on a crime that is often hiding in plain sight in venues such as car boot sales and our town centres.
“That is why we will continue to take the strongest action we can against those trying to sell these harmful and illegal products and work with the police to bring them to justice.”
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Investigating officers are now working to identify the tools and return them to their original owners.
Any tradespeople or those in possession of power tools are advised to mark their property, take photographs, and record serial numbers so that, in the event of theft, officers have more chance of returning property.
If you suspect anyone of selling stolen or counterfeit goods, you can report this to police online or anonymously to the independent charity Crimestoppers by calling 0800 555 111.
