Three men have been arrested for allegedly stealing envelopes at a Long Island post office where residents had previously complained about a check-washing scam.

Police say they watched the three men drive up to the Merrick Post Office on Fisher Avenue early Monday morning as part of a stakeout involving the postal inspection service.

Noah and Ralph Aranzamendi, of Brooklyn, are accused of opening a mailbox and stealing all of the envelopes inside.

News 12 is told detectives came in and arrested the two.

Angel Martinez, of the Bronx, allegedly drove away from the scene and was arrested a short time later.

Investigators say the thieves had a special post office key that could open the mailboxes up.

Maureen McGovern had checks stolen from the same mailboxes. Hers were washed and cashed for nearly $10,000.

"I'm very pleased that there were arrests but I believe it's still just the tip of the iceberg," McGovern said.

Noah Aranzamendi was apparently part of another theft last week at the same post office, authorities say.

Glen McKechnie, of the U.S. Postal Inspection Services, says another person was found fishing in the mailbox using a homemade device earlier in the month.

"Generally it's placed on some type of belt, a sticky glue trap or taper that has some type of adhesive to it," McKenchie said.

It's not clear how the mailbox key got into the hands of the suspects but McKenchie said they sometimes get lost or stolen.

The arrests come nearly two months after a major check-washing scam was revealed at the same location.

The suspects are facing several charges, including grand larceny. They could also possibly face federal charges.