The U.N. health agency also cautioned the contaminated medications may have been distributed outside of the West African country with global exposure “possible."
WHO chief Tedros Adhanom Ghebreyesus told reporters the four cold and cough syrups in question "have been potentially linked with acute kidney injuries and 66 deaths among children."
The four products include Promethazine Oral Solution, Kofexmalin Baby Cough Syrup, Makoff Baby Cough Syrup and Magrip N Cold Syrup, according to the WHO.
Ghebreyesus said the WHO is conducting an investigation “with the company and regulatory authorities in India.”
On Thursday, Gambian authorities began collecting paracetamol and promethazine syrup from rural households in the West Coast Region and Upper River Region.
A Gambian health ministry investigation, which began in July and is ongoing, also cited the E. coli bacteria as a possible cause of the acute kidney failure outbreak.
"The preliminary results from the ongoing investigation indicate that it is most probably the paracetamol and promethazine syrups that caused the acute kidney injury cases in this outbreak," Abubacarr Jagne, the nephrologist leading the health ministry's investigation, told AFP Wednesday.
Health authorities had on September 23 ordered a recall of all medicines containing paracetamol or promethazine syrup.
The Gambia experienced its severest flooding in years in July, causing sewers and latrines to overflow.
"Since July 2022, there has been an increase in the number of severe kidney disease with high fatality among children mainly following diarrheal diseases," the ministry said in a statement in September.
E. coli bacteria were found in the stools of many children, but many had also taken paracetamol syrup, it said.
"To date, the stated manufacturer has not provided guarantees to WHO on the safety and quality of these products," the Wednesday alert said, adding that analysis of samples of the products "confirms that they contain unacceptable amounts of diethylene glycol and ethylene glycol as contaminants."
Those substances are toxic to humans and can be fatal, it said.
The WHO said information received from India's Central Drugs Standard Control Organisation indicated that the manufacturer had only supplied the contaminated medications to The Gambia.
"However, the supply of these products through informal or unregulated markets to other countries in Africa, cannot be ruled out," the U.N. agency said in an email.
"In addition, the manufacturer may have used the same contaminated material in other products and distributed them locally or exported," it warned.
"Global exposure is therefore possible."