A Sioux Falls Credit Union is sounding the alarm on check-washing scams.

SIOUX FALLS, SD (KELO.com) — A Sioux Falls Credit Union is sounding the alarm on check-washing scams.  Thieves are stealing checks from mailboxes, changing the amounts and then cashing them.  Levo Credit Union manager Mitch Eichhorn says they’ve seen three cases this summer and the trend appears to be growing.  He says you should use secure drop boxes, pay online and consider writing checks with gel pens to prevent tampering.