The collection boxes weigh about 200 pounds and are bolted into concrete. (Los Angeles Times )
A recent spate of postal box thefts has put postal authorities on high alert and raised concern that customers may be vulnerable to identity theft.
But authorities said it was unclear whether the brazen heists were part of a trend.
"The economy the way it is, there is an increase in crime all around," said U.S. Postal Inspector Renee Focht of the Postal Service's Los Angeles division, which has jurisdiction over Southern California. "We can't speculate why the mailboxes are being targeted."
Focht said fewer than a dozen of the boxes had been stolen in Southern California since the beginning of June.
As well as being swiped from in front of post offices, the blue collection boxes, which weigh about 200 pounds, had been uprooted from residential neighborhoods and business parks, Focht said.
"It does take some effort," said Focht said. "They're bolted into the concrete."
Four of the boxes were taken in less than a week from several San Fernando Valley post offices, including in Pacoima, Glendale and Burbank.
Local law enforcement agencies would not comment on the thefts because postal-related crimes are investigated by federal authorities.
Focht said authorities had not yet determined whether any of the thefts were linked.
The postal official acknowledged that the stolen mail could be used for identity theft, but noted that only 4% of identity theft cases are attributed to mail theft.
Focht advised postal customers to deposit mail before the last collection time to ensure that items are not left in postal boxes overnight, when thefts might be more likely to occur.
In published tips to help people avoid being victims of identity theft, the Los Angeles Police Department advises residents to have new checkbooks sent to a post office box or arrange to pick them up at their bank.
Authorities also advise people to pay bills through an electronic payment service. Envelopes containing payments should be mailed inside a post office, rather than at a neighborhood postal box.
The Postal Service has offered a $10,000 reward for information leading to an arrest in the San Fernando Valley thefts. Anyone with information is asked to call (877) 876-2455.