Ridgefield police have warned residents to take precautions against mail theft after investigating four incidents where checks were stolen from outgoing residential mail boxes.

“The stolen mail envelopes had checks inside of them that were then altered in an attempt to cash them,” said Ridgefield Capt. Shawn Platt.

He said the would-be thieves were unable to cash the checks “due to the banks identifying that the checks were altered.”

In response, the department shared tips on preventing mail theft from the United States Postal Service.

The post office recommends not leaving delivered mail in a mailbox for too long. They also advise depositing outgoing mail close to the pickup time, or arranging for incoming packages to be picked up after they’re delivered.

“If you do not receive a check, credit card, or other valuable mail you’re expecting, contact the sender as soon as possible and inquire about it,” the postal service said.

The postal service also recommends not sending cash through the mail.

Platt said the Postal Inspector was informed of the thefts “and is investigating.”