WASHINGTON (AP) — The head of the Internal Revenue Service told House Republicans on Wednesday that it would take years to provide all the documents they have subpoenaed in their probe of how the agency handled tea party groups’ applications for tax-exempt status.

The comments by IRS chief John Koskinen drew a frosty response from Republicans who run the House Government Oversight and Reform Committee, one of several congressional panels investigating the controversy. The panel’s chairman, Rep. Darrell Issa, R-Calif., warned him he should comply with the request “or potentially be held in contempt” of Congress, a sometimes threatened but seldom-used authority.