The building collapsed before dawn on Sunday during a thunderstorm in Angeles City in Pampanga province.
More than 100 police and other government personnel were scrambling to rescue those believed trapped in the rubble, Police Brigadier General Jess Mendez said.
Jay Pelayo, who heads Angeles City's information office, said about 30 to 40 people may still be trapped in the rubble, citing a construction foreman who managed to dash out of the building as it tumbled down.
Eight people in the vicinity were rescued, while 11 others, including the site foreman, managed to escape, Pelayo told DZBB radio on Sunday.
It was not immediately clear what caused the collapse, but the city engineer is reviewing the construction history, he said.
Pelayo also said rescue efforts could be challenging as the structure was made of concrete, making it difficult to move the debris.
Images shared by DZBB showed the building reduced to a heap of concrete and twisted metal, covered in green netting.
"The assessment is not yet finished. The unified command system is still working on it, and it is too early to determine the cause of the collapse, which is still being evaluated," Pelayo said.
"Power lines were hit and were now being secured. We are calling on residents in the area to cooperate with authorities so rescue operations for those trapped are not delayed, and no one else is put at risk," he said.
with AP
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