FALLBROOK, Calif. -- The FBI will be briefed Friday on a San Diego County family that has been missing for almost two months.
Sheriff's Lt. Dennis Brugos said investigators are focusing their search for the McStay family in Mexico, where the FBI has more resources.
Businessman Joseph McStay, his wife, Summer, and their two young sons -- Gianni 4, Joseph Jr. 3 -- were last heard from Feb. 4.
Investigators said surveillance video may have captured images of the Fallbrook family crossing the border on foot. Their white Isuzu Trooper was found in a nearby parking lot.
Investigators also found e-mails indicating the couple had asked about passport requirements for traveling to Mexico with children shortly before they disappeared.
Relatives said it's uncharacteristic of the McStays to simply pick up and leave the country without telling family members.
Tracy Russell, Summer McStay's sister, said the idea that the family may have planned to go to Mexico has made her even more worried.
"I know I should feel a little bit better, but I don't," Russell said. "My mother is distraught. I don't think my sister would torture my mom like that."
She last spoke to her sister on the phone Feb. 4.
Mike McStay, Joseph's brother, said he set up a Web site to field tips about the family's whereabouts and has forwarded any promising information to investigators.
Neither Joseph nor Summer McStay is fluent in Spanish, relatives said. Summer McStay's passport is expired. Their youngest son's birth certificate, required for re-entry to the United States by minors under 16, is with a grandmother, relatives said.
Detectives have no evidence that the family had financial problems or were facing threats.
The couple left their dogs at home and food rotting in their kitchen.