Federal investigators have told Congress that they have recovered data that may include lost emails from one of the pivotal figures in the controversy over the Internal Revenue Service's treatment of tea party groups, congressional aides said Friday.

Frederick Hill, a spokesman for Republicans who run the House Oversight and Government Reform Committee, said the investigators said at a staff briefing Friday that they have recovered up to 30,000 emails to and from Lois Lerner.

A statement from Democrats and Republicans on the Senate Finance Committee was more measured. It said the investigators have recovered data that may include Lerner emails.

The investigators were from the Treasury Inspector General for Tax Administration, which audits the IRS. A spokeswoman for the inspector general, Karen Kraushaar, declined to comment, saying the investigation was continuing.

The investigators ignited a political firestorm in May 2013 with a report saying that IRS agents had given exceptionally close scrutiny to tea party and other conservative groups that applied for tax-exempt status.

Lerner headed the IRS division that processes applications for tax exempt status. She has since retired.

IRS officials have said that Lerner's computer crashed in 2011, destroying an untold number of emails.

Hill said it will take weeks for the investigators to process the information into a usable format and give it to the IRS, which would then review it. By law, the IRS would also have to delete information about taxpayers that is considered private before it can be released to the House Oversight panel, which is headed by Rep. Darrell Issa, R-Calif.

The Senate Finance Committee aides said the investigators will assess if the data can be made readable before it can be turned over to the committee.

They said their committee, which has been conducting a bipartisan investigation of the IRS's treatment of groups, expects to complete its work early next year.