The Enquirer understands up to six specialists have come under the spotlight of the The Competition & Markets Authority.
The CMA launched a probe into possible collusion in the supply of construction services in Britain in March.
Investigators have declined to identify the specific sector or scale of the inquiry but results were expected to be released by the end of this month.
One leading industry source said: “This investigation is centred on the demolition sector.
“There is a lot of nervousness around about this because the CMA is not shy about handing out big fines if they find any evidence of wrongdoing.”