Seven people were transported to local hospitals after a carbon monoxide leak in a Northwest Baltimore apartment made them sick, the Baltimore Fire Department reported.

Department spokesman Chief Kevin Cartwright said rescue crews responded to a report of a strange odor in an apartment in the 400 block of Edgewood Road. He said four people were taken to University of Maryland Hospital and three to Johns Hopkins Hospital — all with injuries that were not life-threatening.

"People were complaining of headaches," Cartwright said. He said carbon monoxide was measured at 60 parts per million — not a deadly level but sufficient to cause symptoms with prolonged exposure.

Carrtwright said fire officials have not yet determined the source of the leak. He said carbon monoxide poisoning is generally a result of incomplete combustion of fossil fuels in household appliances such as furnaces and hot water heaters.