The rat infestation at Occupy D.C. has become so serious that protesters should be cleared out of their encampment at a federal park near the White House, said Washington Mayor Vincent C. Gray.

Conditions at the encampment are a "threat to the health and safety of both protesters and district residents," Gray said in a letter to the National Park Service. "Rodents have been seen not only around the site, but inside tents and even in the food preparation area."

At a minimum, the mayor said, the protesters who have been living in tents at McPherson Square for more than three months should be consolidated with another encampment at nearby Freedom Plaza to allow crews to clean up the park and eliminate the rat infestation.

A report by the District of Columbia Health Department says Freedom Plaza is "the more organized’’ Occupy D.C. site, "with a greater attempt being made to adhere to good sanitary practices with waste disposal and food preparation."

Because McPherson Square is federal property, the decision rests with the park service. There was no immediate response from the agency to Gray's letter.

The mayor's office also is seeking reimbursement from Uncle Sam for its $1.6 million in costs, such as police patrols, in dealing with the Occupy D.C. sites.

Concerns about the McPherson Square site were further heightened this week after a 13-month-old baby was left alone in a tent at the encampment for at least half an hour with the temperature in the mid-40s.

Nearby protesters heard the infant crying and called police. A man who said he was her father has been charged with child cruelty.

The D.C. Health Department said in a report that although Occupy D.C protesters contend the man was not part of their group, "the ongoing mixture of homeless, people suffering from mental illness and protesters continues to exacerbate unsafe conditions" at the encampments.

The cold also is a growing concern, Gray said, noting that makeshift heaters that some protesters are using to heat tents have created the risk of carbon monoxide poisoning.

It's an awkward problem for Gray, a protester himself who was arrested last year at the U.S. Capitol, charged with blocking Constitution Avenue in an act of civil disobedience. He was among a group demonstrating against congressional dictates on the district, such as a measure preventing it from spending its own funds on abortions for low-income women. He said such measures "violated the rights of district residents to autonomy and self-determination."

Health officials have advised the protesters on how to keep sanitary conditions, and one Occupy D.C. demonstrator said earlier this week that those in the park are working to clean it. But he added, "There have always been rats in downtown D.C."

Rep. Darrell Issa (R-Calif.), the chairman of the House Oversight and Government Reform Committee, has been upset about the encampment in a park that recently underwent $400,000 in taxpayer-funded improvements. He called Gray's description of the conditions at the McPherson Square "a blunt assessment of the situation created by the National Park Service's decision to ignore laws designed to protect the public.''

Issa has given the park service until Jan. 24 to explain how it concluded that the occupation is considered a "24-hour vigil," allowed under park rules, rather than camping, which is prohibited.

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-- Richard Simon in Washington

Photo: The Occupy D.C. encampment in McPherson Square in Washington. Credit: Karen Bleier / AFP/Getty Images