A firm bidding for a contract at Charleston International Airport withdrew its offer Wednesday after questions about Charleston County Aviation Authority board members’ involvement in recommending subcontractors in its bid.

Columbia-based Michael Baker Corp., the firm hired by the airport as its program manager for the $200 million makeover of the airport’s terminal building, decided to withdraw as one of two bidders for the construction administration and inspection contract, the firm announced during an airport committee meeting.

Their letter to airport officials did not give a reason for their withdrawal.

The panel charged with vetting vendors decided not to award the contract to the other firm, Fentress Architects of Colorado, the company designing the airport overhaul. Instead, they decided Fentress and Baker should reconcile differences in their proposals to avoid further construction delays and report back to the committee as soon as possible.

Baker officials confirmed last week that recommendations by certain Aviation Authority members were included in its proposal, and Aviation Authority Chairman Andy Savage launched an independent inquiry to determine which board members might be involved.

Savage said the results of his investigation will be made public.

The airport’s Terminal Redevelopment and Improvement Plan Committee voted 3-2 earlier this month to award the contract to Fentress, but the full Aviation Authority could not make a decision last week, so it referred the issue back to the committee.

The airport is about to undergo an extensive renovation and expansion that includes adding six new gates, a third baggage carousel, consolidated security checkpoints, a dome over the lobby, a new rental car pavilion, relocated offices and numerous other changes by September 2015.

Reach Warren L. Wise at 937-5524 or twitter.com/warrenlancewise.