WASHINGTON - Investigators said Thursday that they have recovered 32,000 e-mails related to a former IRS official at the heart of the agency's tea party scandal.

But they don't know how many of them are new.

The e-mails were to and from Lois Lerner, who used to head the IRS division that processes applications for tax-exempt status. In June, the IRS told Congress it had lost an unknown number of Lerner's e-mails when her computer hard drive crashed in 2011.

At the time, IRS officials said the e-mails could not be recovered. But at a congressional hearing Thursday evening, Timothy Camus, IRS deputy inspector general, said investigators recovered thousands of e-mails from old computer tapes used to back up the agency's system.

"We recovered quite a number of e-mails, but until we compare those to what's already been produced we don't know if they're new e-mails," Camus told the House Oversight Committee.

Neither Camus nor the inspector general, J. Russell George, would describe the contents of any of the e-mails at Thursday's hearing.

The IRS says it has already produced 78,000 Lerner e-mails, many of which have been made public by congressional investigators.

Camus said it took investigators two weeks to locate the computer tapes that contained Lerner's e-mails. He said it took technicians about four months to find Lerner's e-mails on the tapes.

Several Oversight Committee members questioned how hard the IRS tried to produce the e-mails, given how quickly independent investigators found them.

"We have been patient. We have asked, we have issued subpoenas, we have held hearings," said Rep. Jason Chaffetz (R., Utah), chairman of the Oversight Committee. "It's just shocking me that you start, two weeks later you're able to find the e-mails."

The IRS issued a statement saying the agency "has been and remains committed to cooperating fully with the congressional oversight investigations."

The inspector general set off a firestorm in May 2013 with an audit that said IRS agents improperly singled out tea party and other conservative groups for extra scrutiny when they applied for tax-exempt status during the 2010 and 2012 elections.