Reporter Kendra Marr resigned her position Thursday after New York Times writer Susan Stellin alerted Politico editors to similarities between her transportation policy story published Sept. 26 and Marr's story published Oct. 10.

Politico is not saying whether it has completed its investigation into Marr's work after finding seven instances of plagiarism, or whether newsroom staff are provided (or will be provided) ethical guidelines to follow in their work. Chief Operating Officer Kim Kingsley said the Allbritton-owned organization will not comment beyond the letter to readers.

After being alerted Wednesday night, Politico editors examined Marr's work and discovered incidents in which "specific turns of phrase or passages ... bore close resemblance to work published elsewhere. Others involved similarities in the way stories were organized to present their findings. ... Material published in our pages borrowed from the work of others, without attribution, in ways which we cannot defend and will not tolerate."

In a prominent editor's note by John Harris and Jim VandeHei, Politico linked to the seven of Marr's transportation-related stories that were amended Thursday to include proper attribution. The stories also carry editor's notes that explain the changes. Based on the editor's notes appended to stories, material was used from these sources without proper credit:

Six of the stories were published between Sept. 19 and Oct. 10. One of the stories was published July 28.

A commenter on the editor's note about Marr's plagiarism suggests similarities between a June story of Marr's and an April story by Benjamin Spillman in the Las Vegas Review Journal. It's unclear whether Politico editors reviewed that story or will re-examine it as part of a further investigation.

Marr's LinkedIn profile says she joined Politico in August 2009 after two years as a staff writer at The Washington Post. Her Politico bio says the San Francisco native covered financial news for the Post, including the auto industry, and that her work also appeared in the San Jose Mercury News, The Orange County Register and The Miami Herald. Marr graduated from Northwestern in 2007.

In November 2006, Marr was a student of David Protess at Northwestern. During that time, as part of Medill's Innocence Project, Marr claimed to be a U.S. census worker in order to locate a witness in a murder case. Marr told the Chicago Tribune in May of this year that "she regrets using deception":

"I was a student in the class, and I wish I hadn't done it," Marr said. "It wasn't my idea, and as a professional journalist, I haven't misrepresented myself since, nor do I intend to ever again."

Protess said the deception was the idea of Sergio Serritella, a private investigator then working as a teaching assistant with the Medill Innocence Project.

"At the time, there was no law that prevented them from doing that," Protess said. "When I found out it was legal and legitimate, I gave it the green light."

Serritella denied it was his suggestion. In an email after the incident, Protess congratulated Marr on finding the person and tried to calm her fears about getting in trouble.

"I don't see this as a big deal," Protess wrote in the email to Marr. "It's highly unlikely that (the man) will report you to the Census Bureau, and, if he did, those folks have a lot more on their mind than hassling you … Eventually, they'll get bored and leave you alone. And you're right: at least your number didn't show up as 'Medill.'"

Protess' 30-year career at Northwestern has ended, and the university has agreed to release emails he exchanged with student journalists working on the Innocence Project. || Missing word: Craig Silverman says VandeHei and Harris' note "is notable for the fact that it never uses the word plagiarism, even though it’s explicitly about a case of serial plagiarism." | Related: Jayson Blair is not the standard by which to judge journalistic fraud like Marr's