Officials say there are hundreds of thousands of dollars perhaps even a million dollars missing from local synagogues.
Now the FBI is looking into a multi-state mail fraud ring.
"Nobody's going to think to steal from a mailbox. It's a federal crime to steal from the mail," said Alan Hirsch, President of Congregation B'Nai Israel.
As many as 20 checks are thought to have been stolen from the B'Nai Israel mailbox.
"We lost about eight or nine thousand dollars but that's about 20-percent of our budget. That's a lot of money. That's a lot of money to us. We depend on that for all of our expenses," adds Hirsch.
In the tri-state area and in several other states, from as many as 30 synagogues and charitable organizations that Jewish leaders can document, thousands of dollars are missing.
"One check for $12,000 disappeared and went into a strange account," said Assemblyman Dov Hikind.
The checks are endorsed by people; they claim are not connected with the synagogues and then placed in accounts in the banks.
We took our mailbox down that we had in a part of our schul where members come in everyday to use. So now it's making it more difficult for members to give us," said Ronald Weiss of Young Israel Congregation in Flatbush.
FBI officials tell Eyewitness News it is investigating. Just how widespread and who might be suspected is unclear.
"We know money has been transferred to Israel from one account," adds Hikind.
While there is talk of lock boxes and other precautions, at congregation B'nai Israel, the checks from 50 members now pass hand to hand.