The tenders being investigated by the Office of Fair Trading were submitted by Kier Regional between 2000 and 2005
The Office of Fair Trading is investigating Kier as part of its crackdown on construction.
The OFT is investigating 20 tenders submitted by Kier Regional between 2000 and 2005.
A Kier spokesperson said: “These tenders represent a very small proportion of the bidding activity of Kier Regional during the period. Kier is cooperating with the OFT in its investigation.”