People in Alhambra have been warned to be on guard following a spate of mail thefts.
Police are concerned the problem could become even more pronounced in the run-up to the holidays, when more packages, often of high value, are typically delivered.
They say they say thieves are following mailmen around, then strike after they drop off a package.
"(The) suspect comes by, grabs the package and leaves. We had nine in September, nine similar thefts in October and so far in November we've only had two," Sgt. Jerry Johnson of Alhambra Police Department said.
He said residents should make sure someone signs for packages, and also suggest picking them up at the post office or having them delivered at work.
One arrest was made in September, but the thefts continued and investigators believe there are several thieves.
Police are searching for a man seen driving a green Toyota Corolla with Nevada plates in connection with one case.
