Matthew J. Wilson, a junior at Rice University in Houston was last seen Dec. 15, and his silver 2004 Dodge Neon with Oklahoma plates was found June 10 in the 1200 block of Allston Way in Berkeley.
The 21-year-old student is a native of Haworth, Okla., and was studying computer science.
His mother, Cathy Wilson, recently flew to the Bay Area from Oklahoma and joined the search for her son Saturday afternoon, according to Bridget Melson, co-founder of Trinity Search and Recovery.
"People really dig back into memory when they see her," Melson said. "She looks so much like her son."
The group will resume the search at about 2 p.m. today and plans on making stops at University of California at Berkeley as well as Bay Area Rapid Transit stations in Berkeley, San Francisco, Oakland and Walnut Creek.
Melson said there have been more than 10 reported sightings of Matt Wilson in the Bay Area, including several in Walnut Creek within the last week.
Trinity Search and Recovery has handed out fliers to businesses in the area of some of the sightings, and employees reported seeing a man who fit Matt Wilson's description, Melson said.
He is about 5 feet 7 inches tall, weighing 135 pounds with red hair and green eyes. He may have a beard or glasses.
He was last seen by his roommate on Dec. 14 doing dishes at their apartment, according to a timeline posted on a Web site set up by his family, www.findmattwilson.org.
On the night of Dec. 14, Matt Wilson's debit card was used to withdraw $500, and the family's timeline showed that a few days earlier he had purchased matches, charcoal, a car cover and a car window shade from Target and Wal-Mart.
The card has not been used since, and Wilson's cell phone was left in his Houston apartment, according to a Rice University news release. Wilson missed his final exams and failed to visit or contact his family over the holidays.
A total of $25,000 in reward money is being offered by Rice University and Wilson's family for information regarding his disappearance and/or whereabouts, police said.
Trinity Search and Recovery has conducted more than 20 searches in 10 different cases since it was founded.
To participate in the search or donate, visit www.findmattwilson.org or www.trinitylifesolutions.com/tsar/index.htm.