The U.S. Postal Service is investigating a series of mail thefts in southeast Atlanta.

According to residents along Clay Street, the thefts happened on Tuesday.

Investigators said they are not sure who is behind the crime, but someone went through mailboxes, opened letters, stole checks and left the empty envelopes behind.

“I don’t know how many mailboxes have been hit,” said Joe Hardy. Hardy lives on the block.

Initially, residents called Atlanta police for help, but now the U.S. Postal Inspector’s Service is involved because stealing mail is a federal offense.

Off-camera, a neighbor told Channel 2’s Erica Byfield that a woman on the street found most of the empty envelopes in her mailbox.

Some worry the crime could lead to identity theft.

Hardy said the theft got his neighbors’ attention.

“They are spreading the word. Some are mad, some are surprised and shocked. And they are more cautious now that they know that could happen,” he said.