The Filipinos allegedly left the country in July, according to Mayor Rodrigo Duterte of the southern city of Davao, where some of the recruits came from.
Former president Fidel Ramos said last week that about 100 Filipinos were training to be jihadists in Syria.
"I will validate that and take a careful look if there is basis to that so that we can take appropriate action," said Major General Eduardo Ano, an army division commander. "I will ask our intelligence units to check, to verify if that information is valid."
Local terrorist group Abu Sayyaf, which has been linked to the international al-Qaeda network, and the separatist Bangsamoro Islamic Freedom Fighters have pledged allegiance to the Islamic State via videos posted on the internet.
The military previously denied reports about Filipinos being recruited by the jihadist group.