WEST HARTFORD, Conn. (WTNH) — Police are getting more and more complaints about thieves stealing checks from mailboxes. West Hartford is the latest town warning residents about “check washing.” Scammers can empty your bank account before you even know something is wrong.

You think when you drop a check in the mailbox, it will arrive safely. But in West Hartford, people are finding they keep disappearing as part of a “check washing” scam.

“People take big checks and change the amount on it and stuff,” a West Hartford resident named Sarah, who did not want to give her last name, said.

The thieves also change to whom the check is made out. That is what police have heard again and again. They have even seen thieves at work at this post office.

“They had actually been using a string with a sticky substance on the end of it to retrieve mail from inside the post office box,” Capt. Eric Rocheleau, public information officer of the West Hartford Police Department said.

For just that reason, the U.S. Postal Service is phasing out the boxes with the big, fold-down doors, the kind you could fit a string down and fish out an envelope. Instead, they are using new boxes with much smaller openings you cannot fit anything inside. It makes police wonder if some of the thefts come from residential mailboxes, like the ones at the ends of driveways.

However they get the checks, the crooks then go to work changing them.

“They do use a chemical to remove some of the ink,” Rocheleau said. “Just enough so that they can add a new name, a new amount, and quite often they will go and use a fake ID in order to cash that check.”

One customer told us he mailed a big tax check from this post office, and it ended up in someone else’s account. Sarah just did the same.

“I just mailed the IRS a check, so yeah, I hope it gets there okay,” she said with a laugh.

“Check washing” is happening all over the country, and if it happens to you, make sure you tell police.

“A lot of people, we’ve seen, are on social media posting things, but they are not letting us know,” Rocheleau said. “We definitely want to know so we can put a solid case together and track down all the clues that we can.”

The good news is, banks usually reimburse victims for the stolen money. Police suggest trying to pay your bills electronically.

If you think you may be a victim of mail theft, visit these sites: