BOSTON (AP) An error estimating the value of a building forced Big Dig officials to take $67 million from a state transportation fund for other projects to plug the hole in their budget, officials of the underground highway project said.

The officials of the $14.6-billion Big Dig, officially known as the Central Artery and Third Harbor Tunnel project, also announced Sept. 20 that some completion dates have been pushed back.

The Big Dig’s budget shortfall resulted because of an expectation that the sale of the project’s Kneeland Street 10-story headquarters building would bring in approximately $94 million. But the only bid for the former Wang Computer building was less than a third of that amount, according to officials, so the sale was put off.

The Big Dig moved to identify alternative revenue sources, including the $67 million from the state’s Transportation Infrastructure Fund, which funds smaller road and bridge projects, and $27 million from the proceeds of a 2003 sale of a 75-acre parcel in Allston.

In an e-mail response to questions, spokeswoman Mariellen Burns of the Massachusetts Turnpike Authority (MTA), which oversees the Big Dig, said officials identified the problem last year, and informed federal and state officials about plans to use other real estate revenue, as well as money from the state road and bridge fund.

Burns said the state inspector general’s office has yet to sign off on the financing plan.

U.S. Department of Transportation Inspector General Kenneth Mead’s office also has not approved the backup financing plan, which could further delay approval of $81 million in national funds earmarked for completion of the project.

“They are not going to release the $81 million until they’re satisfied,” said Rep. Michael E. Capuano, D-MA, a member of the House Transportation Committee.

Dipping into the transportation fund raised concerns among some community leaders.

“One always hopes that the end is in sight for the Big Dig, and it seems like there’s light at the end of the tunnel, but the tunnel seems to be getting longer,” said Geoffrey Beckwith, executive director of the Massachusetts Municipal Association. “There’s a huge backlog of state projects. This can’t be good news.”

Meanwhile, some completion schedules for the project have been pushed back.

Substantial completion of the project, which was scheduled for Sept. 22, has been pushed back to Oct. 31. And all roadwork connected with the project won’t be finished until May 31 of next year.

Officials blamed various construction problems for the completion delays.

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