Searchers on horseback, in airplanes, driving ATVS, on foot, and police K-9s spent all of Tuesday and a good part of the evening looking for an elderly South Portland woman who was last seen walking along Five Kezars Road in the Oxford County town of Waterford on Monday morning.

A Maine Air National Guard helicopter equipped with forward-looking infrared was also deployed on Tuesday.

In a statement Tuesday night, Cpl. John MacDonald of the Maine Warden Service called on the public to volunteer to help with Wednesday’s search for 77-year-old Ruth F. Brennan. Brennan was last seen around 10:30 a.m. walking toward Melby’s Market & Eatery on Route 35.

Authorities are also asking people who own property in that area to search their land and outbuildings for any signs or Brennan, who has dementia.

Game wardens are warning people who volunteer for the search to be prepared to encounter rough terrain, including thick woods and swamps. Volunteers should arrive at the Waterford Fire Department station, 366 Valley Road, by 8 a.m.

Brennan was known to walk several miles and was in good physical health. She left a camp on Spur Ridge Road Monday morning to begin her walk.

She is 5 feet 2 inches tall, and was last seen wearing a crewneck striped shirt, capri-style bluejeans, a tan hat, light beige sneakers and light green socks. She has brown hair and hazel eyes.

Anyone with information concerning her whereabouts should contact the Maine State Police dispatch center in Gray at 657-3030.