Authorities Sunday were searching for a mentally disabled Petaluma man with a history of disappearing on long bicycle rides who took off on his bike but by nightfall hadn't returned home, Petaluma police said.

John Wirth, 49, has been missing previously and found as far away as Fairfield, St. Helena and Benecia, Sgt. Andrew Urton said.

For the fourth time this year, police issued a public message for people to be on the looking for the 6-foot tall, 180-pound white man with shaggy brown hair, a full beard and blue eyes.

Wirth, known as "Joe," was wearing a long-sleeved blue shirt and possibly a beige baseball cap, sunglasses, black pants and black shoes with green trim, Urton said.

Wirth's family last saw him at 8 a.m. Sunday riding an orange and red BMX-style bicycle, Urton said.

Wirth has a biking routine and usually comes home without incident, aside from a handful of occasions, Urton said.

However in those cases, Wirth appears to have become disoriented due to a traumatic brain injury he suffered 25 years ago from a near-fatal motorcycle crash and cycled far from home.

On July 8, Wirth was reported missing and found three days later in Benecia. Several weeks earlier, he went missing June 17 and was found the next day with his bike in Fairfield.

Wirth somehow made it from Petaluma to St. Helena when he was found 40 hours later, exhausted and hungry, after disappearing May 15.

Anyone with information about Wirth's whereabouts can call Petaluma Police at 778-4372.