LAPD Chief Charlie Beck said during a Friday news conference that Tobias Summers, 30, was seen on border surveillance camera as he crossed over a footbridge into Tecate, Mexico, sometime late last week. The Tecate border crossing is about 40 miles east of San Diego.
Police searched a Tijuana home that they thought Summers might be hiding with a female friend earlier this week, but there was no one there.
"We're concentrating many of our efforts in not only San Diego County, but in Mexico," Beck said.
Summers was charged on Wednesday with 37 felonies, including kidnapping, burglary and nearly three dozen sex-related counts. If convicted, Summers, a parolee with a criminal record dating back to 2002, could face multiple life terms in prison.
Suspected accomplice Daniel Martinez, who was arrested Sunday, pleaded not guilty to one count each of kidnapping and first-degree burglary.
Authorities said they believe 29-year-old Martinez was waiting in a car outside the girl's home while Summers kidnapped the girl on March 27. Martinez then allegedly drove a short distance with Summers and the girl, then left and was not further involved.
The girl was found hours later wandering six miles from her home near a Starbucks in Woodland Hills. She was barefoot, had bruises and scratches, and wasn't wearing the same clothes she had on when she vanished.
"It will be a member of the public that helps us to capture Summers, and when we capture Summers, every one of our children is a little bit safer," Beck said.
Police had previously said that Summers was believed to be in the San Diego area and may have changed his appearance by shaving his head. It was unclear when Summers crossed the border. Mexican authorities are working with the LAPD to find Summers.
Authorities urge anyone with information on the suspect or the case to call the LAPD Robbery-Homicide Division tip line at (213) 486-6890 or Los Angeles Regional Crime Stoppers at (800) 222-TIPS.