The website is undermining the Construction Plant Competence Scheme (CPCS) which covers thousands of machinery operators across the industry.
It is relied on by contractors to prove that operators are qualified to drive kit like excavators and dumper trucks.
A website started-up earlier this year based in Romania selling the right answers to the theory part of the tests for less that than £10.
Scheme owners from the Construction Industry Training Board have been battling to shut down the rogue site.
They won a hearing in April to seize control of the Romanian website’s domain name and planned to close it down.
But it is now operating under a different domain name hosted in America.
Braden Connolly, Head of Product Management at CITB, said: “CITB is working hard with industry and the police to fight fraud in construction.
“The illegal website in question, of which we gained control following legal action, is now being operated from the United States.
“We are working with the US regulator and the company that hosts the website to put a stop to its operations.
“This process does take time but we are determined to shut this site down.”