WASHINGTON (AP) — The Internal Revenue Service's screening of groups seeking tax-exempt status was broader and lasted longer than has been previously disclosed, the new head of the agency said Monday.

In a conference call with reporters, Danny Werfel said that after becoming acting IRS chief last month, he discovered wide-ranging and improper terms on lists screeners were still using to choose groups for careful examinations. He did not specify what terms were on the lists, but said he suspended the use of all such lists immediately.

"There was a wide-ranging set of categories and cases that spanned a broad spectrum" on the lists, Werfel said. He added that his aides found those lists contained "inappropriate criteria that was in use."

Werfel's comments suggest the IRS may have been targeting groups other than tea party and other conservative organizations for tough examinations to see if they qualify. The agency has been under fire since last month for targeting those groups.

His comments also indicate that the use of inappropriate terms on such lists lasted longer than has been revealed previously. A report last month by a Treasury Department inspector general said agency officials abolished targeting of conservative groups with those lists in May 2012.

Werfel said preliminary results of an examination he has conducted of his agency have so far found no indication of improper screening beyond the IRS offices that examines groups seeking tax-exempt status.

He said he believes there was "insufficient action" by IRS managers to prevent and disclose the problem involving the screening of certain groups, but has discovered no specific clues of misconduct.

"We have not found evidence of intentional wrongdoing by anyone in the IRS or involvement in these matters by anyone outside the IRS," he told reporters.

The IRS has provided congressional committees investigating the agency documents related to the screening problems. He said work was continuing on removing sensitive taxpayer information from those documents, and he said he expects them to be released soon.