In a news release issued Monday, the city said the Department of Public Health was notified about these tents last week.
The sites were offering free COVID-19 testing in Center City.
City officials say the testing tent staffers claimed to be funded by FEMA but confirmed over the weekend that was not true.
"When we confirmed with FEMA that they're not funding anything like this, we sent a warning out to the public to let them know to be careful about where they're getting tested, " said James Garrow, a spokesman for the Philadelphia Health Department.
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Two pop-up tents -- one at 13th and Chestnut and another at 15th and Chestnut -- were shut down after the president of Lab Elite was advised that a subcontractor at the sites allegedly claimed to be a FEMA affiliate.
"Saying that Lab Elite was hired by FEMA to do the testing over there, that information is incorrect," said Zishan Alvi, President of Lab Elite.
Alex Pearlstein says he went to one of those tents.
"They told me they were from FEMA and they were doing free testing," he recalled. "They needed my insurance information, so I gave them my insurance information, my email, my address."
He says that was on December 29, and he was promised tests results within 36 hours maybe sooner. When he didn't hear back from anyone, he managed to get an at-home test kit over the counter on New Year's Eve and tested positive.
Residents who see the questionable pop-up testing sites are asked to report them to the Health Department by calling 215-685-5488.
SEE ALSO: Now in effect: What you need to know about Philly's vaccine indoor dining requirement
Meanwhile, on the 100 block of South 7th Street, Action News found a line of people waiting to get a free rapid or PCR test at a facility called Center for COVID Control. We asked a manager if it was authorized by the city.
"Yeah, it's authorized. We wouldn't have a storefront if it wasn't," said the manager who did not give her name.
But the city says it wasn't aware of any such organization doing testing.
"Even if these places are legitimate, we don't know about them and it's tough for us to be able to separate a legitimate organization from a non-legitimate organization," said Garrow.
Action News emailed the offices of the Center for COVID Control but so far we have not heard back.
The city does list a number of agencies on its website that it is currently working with or have been approved to offer testing.
"Our recommendation is if you feel sick, just assume you have COVID, isolate yourself from others and hopefully you'll get over it quickly," said Garrow.
Philadelphia officials say 38% of COVID-19 tests in the city have come back positive in the last two weeks.
The city is averaging 2,654 new cases of COVID-19 per day over the last two weeks, officials said.