NEW YORK – Two people died and two others were critically ill after breathing carbon monoxide fumes in a Manhattan apartment building, authorities said.

Police and firefighters arrived at the building shortly after 10 p.m. Sunday. They found two men dead on the sixth floor, and two women on the fifth floor were hospitalized in critical condition, police said.

The fumes apparently came from a leaky furnace in the building, said fire department spokesman Paul Iannizzotto.

Carbon monoxide is a colorless, odorless gas that can be fatal when inhaled in large quantities.