Two people have been hospitalized and a Detroit-area hotel was evacuated after high carbon monoxide levels were recorded.

Warren Mayor James Fouts says a couple visiting the area from Colorado and their pet dog were found unresponsive Monday at the Hawthorn Suites north of Detroit.

Their names weren't released and their conditions weren't immediately known.

Consumers Energy spokesman Roger Morgenstern tells The Detroit News that initial carbon monoxide readings were about 400 parts per million, which he said could be fatal depending on the length of exposure. The level had dropped to about nine parts per million, generally the threshold for evacuation, by the time a crew from the utility arrived at the hotel.

The hotel's general manager tells TV station WXYZ-TV a housekeeper found the guests.

Authorities are investigating.