E-mail records are missing for 51 of the 88 White House officials who had electronic message accounts with the Republican National Committee, the House Oversight Committee said Monday.

The Bush administration may have committed "extensive" violations of a law requiring that certain records be preserved, said the committee's Democratic chairman, adding that the panel will deepen its probe into the use of political e-mail accounts.

The committee's interim report said the number of White House officials who had RNC e-mail accounts, and the number of messages they sent and received, were more extensive than previously realized.

The administration has said that about 50 White House officials had RNC e-mail accounts during Bush's presidency. But the House committee found at least 88.

The RNC has preserved e-mails from some of the heaviest users, including 140,216 messages sent or received by Bush's top political adviser in the White House, Karl Rove. However, "the RNC has preserved no e-mails for 51 officials," said the interim report, issued by committee chairman Henry Waxman, D-Calif.

The 51 include Ken Mehlman, a former White House political director who reportedly used his RNC account frequently, the report said.

"Given the heavy reliance by White House officials on RNC e-mail accounts, the high rank of the White House officials involved, and the large quantity of missing e-mails," the report said, "the potential violation of the Presidential Records Act may be extensive."

The records act requires presidents to assure that "the activities, deliberations, decisions, and policies that reflect the performance" of their duties are "adequately documented ... and maintained," the report said.

White House press secretary Tony Snow told reporters he would not "respond specifically" to the committee's findings but said the RNC e-mail accounts "were designed precisely to avoid Hatch Act violations that prohibit the use of government assets for certain political activities." He added, "the RNC has had an e-mail preservation policy for White House staffers."

Congressional Democrats are investigating whether White House officials used RNC e-mail accounts to conduct overtly political, and perhaps improper, activities such as planning which U.S. prosecutors to fire and preparing partisan briefings for employees in federal agencies.

Waxman's committee is contacting numerous federal agencies to determine whether their records "contain some of the White House e-mails that have been destroyed by the RNC," the report said.

In a statement, Waxman called the panel's findings "should be a matter of grave concern for anyone who values open government." He said the committee will investigate "who knew about the violations of the Presidential Records Act, why they did not act earlier, and what e-mails can be salvaged from RNC, White House, and agency computer systems."

The report especially criticized Alberto Gonzales, now the attorney general, for actions when he headed the White House Counsel's office. There is evidence that under Gonzales the office "may have known that White House officials were using RNC e-mail accounts for official business, but took no action to preserve these presidential records," the report said.

Snow said of the claim: "That's an allegation. We'll respond to it in due course."

The report said the House committee may need to issue subpoenas "to obtain the cooperation of the Bush Cheney '04 campaign." It said the campaign acknowledges providing e-mail accounts "to 11 White House officials, but the campaign has unjustifiably refused to provide the committee with basic information about these accounts, such as the identity of the White House officials and the number of e-mails that have been preserved."

The House committee report said Rove's RNC e-mail account carried 75,374 messages to or from people with government, or .gov, accounts. It said the RNC has preserved 66,018 e-mails sent to or from former White House political affairs director Sara Taylor, and 35,198 sent to or from deputy director Scott Jennings.

"These e-mail accounts were used by White House officials for official purposes, such as communicating with federal agencies about federal appointments and policies," the report said.

It said the White House counsel in early 2001 "issued clear written policies" instructing staffers "to use only the official White House e-mail system for official communications and to retain any official e-mails they received on a nongovernmental account." Recent evidence "indicates that White House officials used their RNC e-mail accounts in a manner that circumvented these requirements," the report said.