Nigeria reported two cases of chloroquine poisoning after U.S. President Donald Trump praised the anti-malaria drug as a treatment for the novel coronavirus.

Health officials are warning Nigerians against self-medicating after demand for the drug surged in Lagos, a city that’s home to 20 million people. Two people were hospitalized in Lagos for chloroquine overdoses, Oreoluwa Finnih, senior health assistant to the governor of Lagos, said in an interview.

“Please don’t panic,” she said via text message. “Chloroquine is still in a testing phase in combination with other medication and not yet verified as a preventive, treatment or curative option.”

Nigeria’s Centre for Disease Control warned that the World Health Organization hasn’t approved use of the drug against the virus. Africa’s most populous country reported 22 infections as of Saturday.

#FactsNotFear@WHO has NOT approved the use of chloroquine for #COVID19 management. Scientists are working hard to confirm the safety of several drugs for this disease.

Please DO NOT engage in self-medication. This will cause harm and can lead to death.#COVID19Nigeria pic.twitter.com/K6kljq0VtW

— NCDC (@NCDCgov) March 20, 2020

Trump said Thursday that chloroquine and its less-toxic cousin hydroxychloroquine had shown “tremendous promise” to treat the new illness. Hospitals in the U.S. are rushing to stockpile the drug.

The president doubled down on Saturday, telling his Twitter followers that hydroxychloroquine and azithromycin “taken together” could be “one of the biggest game changers in the history of medicine.” He urged they “be put in use IMMEDIATELY.”

The Food and Drug Administration hasn’t approved the antimalarials to treat Covid-19, the respiratory illness caused by the coronavirus.

While chloroquine is no longer used to treat malaria in Africa, some pharmacies still stock it for patients who are resistant to other anti-malaria drugs.