A 3-year-old boy died after being found frothing at the mouth at his Brooklyn day-care center, police sources said yesterday.

Andy Li, of East 12th Street in Bensonhurst, took a nap at about 2 p.m. Saturday, sources said.

Day-care workers found him foaming at the mouth and unresponsive at about 3:25 p.m., cops said.

He was pronounced dead on arrival at Maimonides Hospital.