(CNN) – A top White House official blamed a computer crash for the disappearance of emails from embattled former Internal Revenue Service official Lois Lerner, echoing the explanation the agency gave Congress last week for the two years' worth of missing subpoenaed correspondence.
"I think it's entirely reasonable. And it's fact," incoming White House press secretary Josh Earnest told reporters aboard Air Force One Monday.
"You've never heard of a computer crashing before?" he asked.
After the IRS informed Congress of the missing emails last Friday, Republican lawmakers have accused the White House of a cover-up.
Earnest called those accusations "not at all surprising and not particularly believable," adding 67,000 emails "sent by or received by" Lerner have been offered to Congress.
Lerner, the former director of the IRS exempt organizations division, has invoked her constitutional right not to testify before Congressional committees investigating the agency's targeting of tea party and other interest-specific groups.
House Oversight Committee Chairman Darrell Issa subpoenaed her emails in an attempt to learn whether other agencies were involved in the targeting of those organizations.
The California Republican told CBS on Monday that Lerner's explanation for the missing emails is "just not believable."
"We have enough evidence of her wrongdoing that we want to review every email that she has sent or received. That's reasonable to do when you have someone who takes the fifth," he said.
"This is not about what you turn over. It is all about what you don't turn over."
Issa previously called the crash "convenient" for the Obama administration, adding that the supposed loss of Lerner's documents damages the credibility of claims that the IRS is complying with congressional requests to seek the truth.
In a statement, the IRS said that Lerner tried to recover her emails, which dated from January 2009 to April 2011, after her hard drive broke down but was unable to do so. The agency said it then worked backward to recover the missing emails from recipients of the messages.
CNN's Sara Fischer contributed to this report.