WASHINGTON — U.S. auto safety regulators on Monday closed a six-year-old investigation into 1.47 million Ford Explorers over reports of exhaust odors in vehicle compartments and exposure to carbon monoxide without seeking a recall.

NHTSA said it conducted an in-depth investigation that included review of more than 6,500 consumer complaints from 2011-2017 model year vehicles — including police versions of the large crossover — and found no evidence of a safety issue.

NHTSA said its investigation found “that the 2011-2017 Ford Explorer vehicles when accurately measured produce occupant compartment (carbon monoxide) levels which fall below current accepted health standards.”