Firefighters putting out a blaze in a Brooklyn apartment Friday morning discovered the body of a man who had been stabbed to death, law-enforcement sources said.

Romulo Heras, 61, was found with a stab wound to the neck ­after the fire was extinguished in his ground-floor apartment at 59 Logan St. in Cypress Hills shortly after 9 a.m.

The fire is believed to have started in two areas.