SAN DIEGO -- One or more thieves broke into a U.S. Postal Service van in City Heights Tuesday and made off with two trays of mail, authorities reported.

The smash-and-grab in the central San Diego district occurred in the mid-morning, USPS spokesman Mike Cannone said.

The letter carrier on the route -- who was away from the vehicle when the crime occurred and returned to find one of the windows shattered – told investigators the stolen bins were each about one-quarter full.

Cannone estimated the loss at roughly 80 pieces of mail.

Postal officials will send letters to potentially affected residents to alert them to the situation, Cannone said.

Thieves who steal mail generally are trying to get their hands on checks, credit cards and other items they can use for illicit monetary gain, the spokesman added.