PHOENIX -- A new report by the U.S. Census Bureau said Arizona and other states have fewer undocumented immigrants than last year.

The study cited the economy as the main reason that states like Arizona have become less attractive to undocumented immigrants, but Hispanic advocates also said there is no doubt some are afraid of increased efforts to crack down on illegal immigration.

"I'd say in the past six months, there has been a trend of undocumented immigrants going back to Mexico because they're afraid," said immigration attorney Maria Jones.

In particular, Jones said undocumented workers are afraid of the Maricopa County Sheriff's Office, which has made fighting illegal immigration a priority in the past few years.

"I believe this illegal immigration fight is paying off overall by reducing crime," said Sheriff Joe Arpaio.