Authorities are looking for a mentally ill 21-year-old man reported missing Monday in Belmont.

Shant Vogt, of Calabasas, was last seen by his parents around 9:30 p.m. on Oct. 25 at the AM/PM Mini-Market at 470 Ralston Ave.

He was wearing an olive, green and brown patchwork baseball hat, white suit jacket with a black cross on the back, red and orange tie-dyed T-shirt and long black denim shorts with green trim. He is 5-foot-7, weighs 140 pounds and has brown hair and blue eyes.

Police said Friday that witnesses who believe they spotted the man recently in South San Francisco said he appears to now be wearing a brown jacket.

Vogt was visiting the Bay Area with his parents, who dropped him off at the gas station and expected him to return to the nearby Motel 6 where they were staying. They told police he wanted to go to the Haight-Ashbury district in San Francisco and have been putting up fliers around the neighborhood since he went missing.

Vogt's parents told police he has the mental age of a 15-year-old and was not carrying medication with him. He did not have any money or credit cards.

"We have no reason to believe he was abducted or anything like that," Belmont police Lt. Pat Halleran said. "He could have just decided to go somewhere else."

Vogt goes by the nickname Shanti and sometimes uses the alternate last name Furuli-Vogt.

Anyone seeing a person matching his description should call 911.