Swampscott Police are warning residents about stolen mail— particularly checks— from mailboxes.

The region-wide issue was brought to light when resident Sally Clapp revealed that she had a check stolen from a U.S. Postal Service collection box outside the Swampscott Post Office.

“We just had a check stolen from the mailbox in front, altered and cashed to the tune of $5,000,” Clapp said in recent Facebook post in the community group “Swampscott Nest.” “The bank told us that four more people came in right after us with the exact same (issue) from the same post office. This is really happening.”

The post garnered a fair amount of attention, with more than 84 comments from other community members. Many expressed that they have experienced a similar situation.

Det. Mike Chandler said that the police department is looking into the issue, with more than 15 active cases currently.

“Mailbox fishing or check washing is basically what it’s called,” Chandler said. “People are taking legitimate checks and washing them of their information… changing all the information from the payee, to the amounts and locations.”

Chandler suggested a number of solutions to lower the risk of falling victim to the crime, including mailing directly from the post office as opposed to mailboxes, using direct deposit with employers instead of being paid by check, and shredding important documents in favor of throwing them in the trash. Chandler added that using a specific type of pen can prevent the check from being altered.

“When writing a check, use a gel pen. The ink from the gel soaks further into the paper, making it more difficult,” Chandler explained.

Chandler believes that as of right now, the best long-term solution to the issue is raising public awareness.