A baby is in serious condition after a fire tore through an three-story apartment building in Brooklyn Wednesday afternoon, police sources said.

The blaze broke out on the second floor of the East Flatbush building on Church Avenue near E. 48th Street around 2:59 p.m., and was under control about a half-hour later.

“The flames came rushing out of window, all the way up to the third floor. The flames were intense, just shooting out the window,” said witness Dennis Royal, who works across the street.

The baby and four adults, with minor injuries, were taken to Kings County Hospital.

The cause of the fire is under investigation.