BRUNSWICK – Angry over delays and a paucity of data, Sen. Susan Collins said Thursday the Committee on Homeland Security and Governmental Affairs is preparing subpoenas to force the Pentagon to turn over more base closing documents.

Collins, the committee’s chairwoman, said the subpoenas could be issued by week’s end if the Pentagon declines a final request to release additional data used in its recommendation to close about 180 military installations across the country.

“I do believe I will issue the subpoenas before the end of the week,” Collins, R-Maine, said after four base closing commissioners toured the Brunswick Naval Air Station, one of three major military facilities targeted to be either scaled back or closed in Maine.

The Pentagon came under fire for missing its May 23 deadline to release the data used to support its base closing recommendations.

Officials promised to release much of the data to congressional staffers who have security clearances this week. But data made available at a secure location Tuesday night was “insufficient,” Collins said.

Those documents made available by the Pentagon included minutes from meetings of people involved in the decision-making process, but Collins said she wants more information, including e-mails and specific economic data.

Also, Collins said, the Pentagon needs to declassify more of the documents so they can be made public and used at public hearings. The Base Realignment and Closure Commission is holding a hearing on July 6 in Boston.

The independent commission reviewing the Pentagon’s base closure proposals agreed to delay a regional hearing in St. Louis after dozens of senators complained they needed more time to review new data justifying the plans. The hearing, originally scheduled for June 7, was delayed indefinitely, said Missouri Sen. Kit Bond.

Defense Secretary Donald Rumsfeld said the Pentagon was working as quickly as possible to sort through which data can be released and which are classified.

“The task of going through that enormous digital database and determining what’s classified and what isn’t is something that will take a few more days,” he said Wednesday. The Pentagon had no further comment on Thursday.

Collins and Sen. Joseph Lieberman, the committee’s ranking Democrat, sent a letter to Rumsfeld last week warning that they would resort to subpoenas if necessary. Only a complete release of data including e-mails, memoranda, spreadsheets, analyses, raw data, handwritten notes and telephone logs is acceptable, they said.

Collins said Thursday she planned to confer with Lieberman before a final decision is made on subpoenas. Logistics would require that the subpoenas be signed by Collins, so they would have to be sent to Maine before they could be served.