Published: Sep 21, 2010 7:43 PM EDT
Updated: Sep 21, 2010 4:43 PM EDT

LAND O'LAKES, Fla. (AP) - Authorities issued a Silver Alert for a missing Gulf coast area 80-year-old man who drove off in a housekeeper's car.

Authorities on Tuesday said Charles Graham Porter has Alzheimer's disease. He is 6 feet tall, has white hair and wears glasses. He was last seen wearing a white polo shirt, black shorts and white tennis shoes.

Authorities say he took off in a blue 2000 Ford Expedition with a Florida tag H971GA. They ask anyone who may see Porter or the vehicle to contact the Pasco Sheriff's Office or their local law enforcement agency.