(CNN) -- Police arrested a man Sunday in Escondido, California, in connection with the disappearance of a 17-year-old girl, according to the San Diego County sheriff.
Specific charges have not yet been filed against John Albert Gardner III, a 30-year-old registered sex offender, but Sheriff William Gore said at a news conference that physical evidence links Gardner to Chelsea King. He declined to elaborate.
King has been missing since Thursday when she failed to return home from an after-school run, according to CNN affiliate KGTV.
Gore said the investigation is ongoing.
"Our primary goal has been to find Chelsea King," he said. "We are continuing those efforts."
He added that authorities are holding out hope King will be found alive.