RIVERSIDE (KTLA) -- Two utility workers have been fired after investigators found they had been making up fake numbers for meter readings.

The two workers were put on surveillance after Riverside Public Utilities received a higher-than-usual number of complaints of incorrect bills over the summer.

Investigators found that the workers spent the majority of their shift inside trucks, using made-up numbers instead of checking meters.

The computer systems used by workers are meant to flag errors immediately, Utilities General Manager David Wright told the Press-Enterprise.

It is unknown if the workers knew the other was also skipping meter readings. Wright assumed they merely didn't feel like walking their routes.

The names of the workers were not released because the city does not release details in personnel matters.

Officials believe hundreds of customers were affected. All issues with late or incorrect bills have been fixed.