BOISE, Idaho (AP) — Authorities say an 18-year-old Marine whose body was found in a Meridian apartment died from acute carbon monoxide poisoning. McQuen Forbush's girlfriend found him unresponsive on the apartment's bedroom floor Saturday afternoon. The Idaho Statesmen reports ( ) the Ada County Coroner's report lists the time of death as 3 a.m. Police Deputy Chief Tracy Basterrechea says the gas-fueled heating system was the only possible source of carbon monoxide identified in the apartment, but the equipment appeared to be operating as it should. Basterrechea says investigators will try to recreate other variables to find out what went wrong. Police said Tuesday the apartment had a carbon-monoxide detector but it did not have any batteries in it.