MILL VALLEY, Calif. -- Authorities are investigating whether a body found in a marsh near Mill Valley Tuesday afternoon is that of a 72-year-old woman who was reported missing from a care home facility in the city Monday evening, according to the Marin County Sheriff's Office.

Elizabeth Harrison, who also goes by the name Betsy, was last seen leaving The Redwoods at 40 Camino Alto, Lt. Doug Pittman said. She has a slight onset of dementia, sheriff's Sgt. Debra Barry said.

An active search was initiated in Marin County led by the Mill Valley Police Department, Marin County Sheriff's Office Search and Rescue and Southern Marin Fire Department.

Barry said the investigation into Harrison's whereabouts led police to the discovery of the body of an elderly female around 4:30 p.m. in a marsh behind the Holiday Inn Express at 160 Shoreline Highway.

The body has not been identified and Barry said the cause of death has not been determined.

Anyone with information regarding the case is advised to call Pittman at (415) 747-2191.