Plus, the department said, providing the requested documents would break a "long-standing" agreement between Congress and the executive branch not to seek internal communications because such disclosures could stifle candid debate.

The Labor Department's acting solicitor general, Jonathan Snare, wrote committee chairman George Miller, D-Calif., on Friday saying the department was "surprised and disappointed" by the subpoena and accusations that the department was stonewalling the committee's investigation.

"This was a disturbing development," Snare wrote of the subpoena issued Sept. 24, adding that the department has turned over nearly 15,000 pages of documents in less than 30 days since the committee's first request.

Miller's committee - which this week heard testimony from family members of the nine miners and rescue crew members killed at the Crandall Canyon tragedy - is conducting one of three congressional probes looking into the disaster in rural Utah and mine safety nationwide. Miller had complained that the Labor Department was not complying with his demands and gave the department until Tuesday to turn over a slew of records.

The department did not flatly refuse to respond to the subpoena but did say it would be impossible to comply with all of the committee's demands. Late Friday, a department spokesman said that it would be turning over 200,000 e-mails to the committee before the Tuesday deadline.

Miller's office has received the letter and is reviewing it before deciding how to respond, said spokesman Tom Kiley.

Snare previously asked the committee to delay interviews and public testimony of some involved to prevent clashing with the department's ongoing investigation. Miller refused, saying his committee has an important oversight role especially after a major disaster.

Friday, Snare said it could take up to 20 weeks to comply with the committee's subpoena and the department likely would have to hire a private contractor to search through blocks of records and archived e-mails, an action that could cost some $3.5 million.

Snare adds that the department has concerns about turning over any internal communications, citing an informal agreement between Congress and the executive branch to keep those documents private.

"Such disclosures could have a substantial inhibiting effect" on future internal communications, Snare said.

Two of Miller's requests, Snare noted, came while rescue efforts were still ongoing at the mine. Staffers in district offices were busy with the disaster aftermath and unable to quickly comply with the committee's demand. Even before the letters asking for a load of documents, Miller's committee staff had made "multiple related verbal and e-mail requests," including many on Aug. 6, the day of the mine cave-in, Snare wrote.

Six miners were trapped in a tunnel collapse about 1,900 feet underground that morning when walls of coal burst in what is known in the industry as a bounce or bump. Three rescue workers were later killed and three others injured attempting to find the trapped miners, still entombed in the mountain.

In addition to Miller's committee, the Senate Appropriations subcommittee on workplace safety is probing the disaster, along with the Senate Health, Education, Labor and Pensions Committee.

tburr@sltrib.com