The Boston Fire and Police departments report a man in his 20s was found dead in a car outside 57 Woolson St. in Mattapan around 4:20 p.m. on Saturday.

Authorities say the man, who may have gotten in the car as early as 11 a.m., may have died from carbon monoxide poisoning due to a blocked exhaust pipe.

Earlier in the day, a boy on Nazing Street was pronounced dead after he took refuge from the chill of snow shoveling inside his father's running car.

Authorities urge residents to ensure exhaust pipes are not blocked before they start their cars and get in them.