At least 1,925 people in the southern Philippines, most of them schoolchildren, were sick after eating the fruit-flavoured candy and 66 remain hospitalised, health department spokesperson Lyndon Lee Suy said.
The department's experts "are trying to investigate and consider all possible causes. It could be intentional, it could be mishandling," he told AFP.
The victims complained of stomach cramps, diarrhoea, vomiting and headaches after consuming the durian-, mango- and mangosteen-flavoured treats that were sold by vendors outside schools.
The number of people affected jumped by 600 from those initially reported when hospitals on the southern island of Mindanao began treating patients on Friday.
The government's Food and Drug Administration said it was looking into possible contamination involving staphylococcus, salmonella or E. coli bacteria, with test results available on Wednesday at the earliest.
Police have arrested nine street vendors who obtained the sweets from the same producer -- Wendy's Delicious Durian Candy. The owner of that company, Janet Aquino, is also under investigation after turning herself in to police.
Senior Superintendent Narciso Verdadero, chief of police in one of the affected provinces, said the vendors will likely be charged for violating consumer safety laws.
"The owner is not yet off the hook because many violations have been spotted like (the lack of) expiration dates on the products and proper labelling," he added.
The health department called on the public to be on guard for spoiled or unsafe food being sold, particularly repackaged food items peddled without proper labels.
The Philippines' southeastern region is famous for producing tropical fruits, which are transformed into a range of food products including confectioneries, jams and ice cream.
Poor enforcement of food safety regulations has been blamed for past cases of food poisoning in the Philippines, an impoverished nation of 100 million people.
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ