NEW YORK (CNN) - The editor of USA Today resigned Tuesday, one month after the newspaper reported that a team of its journalists had found "strong evidence" that Jack Kelley, one of its former star reporters, made up portions of stories, plagiarized and lied.

In an e-mail to the staff at the McLean, Va.-based newspaper, Karen Jurgensen, 55, wrote, "Like all of us who worked with Jack Kelley, I wish we had caught him far sooner than we did. The sad lessons learned by all in this dreadful situation will make USA Today a stronger, better newspaper."

Kelly has denied the accusations.

The announcement of the resignation, effective immediately, was made at 5 p.m. ET.

On Monday, the newspaper reported on its front page that seven weeks into an examination of Kelley's work, "a team of journalists has found strong evidence that Kelley fabricated substantial portions of at least eight major stories, lifted nearly two dozen quotes or other material from competing publications, lied in speeches he gave for the newspaper and conspired to mislead those investigating his work."

Kelley, 43, resigned in January after admitting he conspired with a translator "to mislead editors overseeing an inquiry into his work," the newspaper said. Kelly, however, has denied fabricating stories or plagiarizing.

Asked about the role of Kelley in Jurgensen's resignation, spokesman Steve Anderson said, "You're going to have to read into it what you're going to have to read into it. Unfortunately, my hands are constrained at this time as to what I can say."

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In an e-mail to staff members, publisher Craig Moon said, "For 21 years, Karen worked tirelessly to build USA Today into the nation's largest newspaper. She has been meticulous in every detail since becoming editor" in May 1999.

"As a result of her efforts, Karen has improved both the prestige and the content of the newspaper. She will be missed."

A search for a new editor is under way, he said.

"I don't know anyone at this newspaper who won't be saddened by Karen's departure," said Brian Gallagher, the paper's executive editor. "Both personally and professionally it is a great loss."