Products in more than 15,000 stores, including Dollar Tree, Dollar General and Family Dollar, are being questioned.
The Food and Drug Administration says it sent warning letters to Dollar Tree from 2016 to 2019, warning the company about potentially faulty products from Chinese manufacturers.
In some cases, investigators found rat feces inside the manufacturing plants.
Despite the warning by the FDA, a Dollar Tree store on University Boulevard in Jacksonville continues to sell unsafe over-the-counter medication.
People who shop at Dollar Tree were surprised by the warning.
"I've gotten aspirin, ibuprofen, things like that but, now, hearing this," Ricardo Garcia said.
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"I'd be very upset if my health were at risk for financial gain," Deb Marett said.
"That's the first I heard of it," Tonya Wells said.
The FDA says Dollar Tree was warned two times before and earlier this year.
The warning letter it sent the Dollar Tree's parent company says the Chinese manufacturers it imports medications from didn't meet FDA standards.
The agency says drugs were not tested.
Ricardo Garcia said he is hopeful that whatever isn't safe will soon be removed.
"We don't come to Dollar Tree and think we are going to get poisoned," Garcia said.
Action News Jax reporter Jamarlo Phillips went inside the Dollar Tree store on University Boulevard to check and found the shelves were full of assured brand medicine.
Many of the medications in questions are topical, such as muscle rub medications.
"It's just not fair for the people who are less fortunate," Garcia said.
"My hope is that they'll do the right thing," Marett said.
In a company statement, Randy Guiler, the vice president of investor relations at Dollar Tree, said, "We are committed to our customers' safety and have very robust and rigorous testing programs in place to ensure our third-party manufacturers' products are safe."
Now, the company has 15 days to respond to the FDA and develop a system to make sure it corrects the problem.
"I think it is very necessary for them to clean it off the shelves or close the store down," Garcia said.
The FDA says it could take legal action if the company doesn't comply.
The Dollar Tree company says it is cooperating with the FDA and plans to meet with the agency very soon.