MINNEAPOLIS (WCCO) — Roseville police conducted an undercover sting operation to try to find out who’s been stealing mail.

Last week, they put a decoy package in a mailbox. Then, a car pulled up and a woman took the package.

Police stopped the car and arrested three people in it.

Among the items found in the car were chemicals used to remove ink from stolen checks.

There was also a journal that said “Places to Hit Mailboxes,” and it listed St. Paul Park, Newport, Cottage Grove and cities along Interstate 94, along with a reminder to “learn the area for possible getaways.”

Police say the three suspects admitted to being involved in the thefts, and cashing altered checks.

A 32-year-old man, 31-year-old woman, and 50-year-old woman, all from St. Paul, have been released pending further investigation.

Police say they are linked to other mail thefts in the metro.

There at least 20 victims.