West Springfield, AL- A man and woman found dead in a home under construction in West Springfield earlier this week apparently died of carbon monoxide poisoning, authorities said.

Stephen W. Castle, 48, and Mary Holmes, 52, were found at about 6:30 a.m. Monday inside the home by a mortgage company appraiser, police said.

The pair were found on the second floor of the house near a stairway, Sgt. Daniel M. O’Brien said.

It is believed Castle and Holmes went to the building Saturday to work on the house, Deputy Fire Chief William M. Flaherty said.

When police arrived, they had to open windows because carbon monoxide levels were too high, O’Brien said.

It appears the carbon monoxide came from a gasoline-powered generator in the garage, Flaherty said. The generator had no gasoline in its tank when police arrived.

When police and fire investigators ran the generator, the carbon monoxide produced was higher than safe levels after only five minutes, Flaherty said.

The exact cause of death will not be determined until after autopsies.