"Dozens of children have died in the last three months," Gambia's director of health services, Mustapha Bittaye, told Reuters. "Autopsies suggest the possibility of paracetamol."
A spike in cases of acute kidney injury among children under the age of five was detected in late July.
Symptoms including an inability to pass urine and a fever can within hours end in kidney failure.
It was not yet clear if one brand of paracetamol was under investigation. Bittaye said it was likely a syrup sold locally.
In a statement last week, Gambia's health authorities said that this kind of illness often has more than one cause.
E. coli bacteria was also a possibility, Bittaye said.
In an update a month ago, the health ministry reported 28 deaths. Bittaye said that the number was much higher now.
An official tally is expected in coming days, he said.