Bryant Wong, a disaster-response officer, said dozens of ambulances transported at least 244 people who either vomited or grew dizzy hours after eating a breakfast of chicken stew with egg and rice and drinking water in a sports centre in suburban Pasig city, Manila.
Food and Drug Administration personnel took samples of the food to check if it caused the apparent poisoning.
The incident cut short what was supposed to be a day-long celebration by more than 2,000 Marcos followers, Mr Wong said.
Images showed chaotic scenes, with people lying on the floor, scores of medical workers working frantically to tend to them and a fleet of ambulances – sirens howling – lining up outside the venue.
Imelda Marcos’s son, Bongbong, apologised and promised to help those who fell ill until they fully recover.
Imelda Marcos, who ended her term in May as a member of the House of Representatives, celebrated her birthday on Tuesday.
Her daughter, Imee, ran successfully for a Senate seat in the May 13 local and congressional elections.
He died in self-exile in Hawaii in 1989, while his widow and children made an impressive political comeback.
Mrs Marcos drew international condemnation for her massive collection of shoes and expensive jewellery she left behind after they were overthrown.
