WASHINGTON - President Obama's pick to head the Social Security Administration could be stalled over the agency's handling of a $300 million computer project that doesn't work.

A group of Republican senators said Wednesday they will try to block the nomination of Carolyn W. Colvin until an investigation into the troubled computer project is concluded.

A senior Democratic senator agreed that Colvin's confirmation should be delayed until she answers questions about the project, increasing the likelihood that a vote will be pushed into next year, when Republicans take control of the Senate.

All 11 Republican members of the Senate Finance Committee signed a letter to Colvin Wednesday. They said there is evidence Social Security officials may have misled Congress and investigators about problems with the computer program, which is supposed to help workers process and manage disability claims.

Colvin has been the acting commissioner since February 2013. Before that, she was deputy commissioner for 31/2 years. Obama nominated her to a six-year term in June.

"We cannot in good faith allow a nomination for any position that requires the advice and consent of the Senate to proceed to a vote as long as the specter of a potential criminal investigation surrounds the nominee and/or those in their inner circle," wrote the senators, led by Sen. Orrin G. Hatch of Utah, the top Republican on the Finance Committee.

"Therefore," the senators wrote to Colvin, "it is essential to address your role with respect to this inquiry before each of us can make an informed decision on how to vote for your nomination once it reaches the full Senate for consideration."

A Social Security spokeswoman said in an e-mail: "Carolyn W. Colvin is not personally the subject of any criminal investigation."

"Agency representatives previously briefed members of the Senate and House regarding the issues raised in the Senate Republican Finance members' letter," said the agency spokeswoman, LaVenia LaVelle. "The acting commissioner will respond timely and fully to the members' requests, and continue to cooperate with Congress and any related investigation."

LaVelle noted that the agency just received the senators' letter Wednesday afternoon.