Dayton police are investigating after a rabbi brought them a mysterious envelope Monday night.

Police said the rabbi brought the envelope to Fifth District Police Headquarters saying his address was marked as the return address but that he had not sent the letter.

He told police the address it was sent to was a synagogue that is no longer open on Salem Avenue.

Police said the letter was unusually thick and soft and they believe it contained something other than paper.

Police said they called the Dayton Fire Department to take the letter until it could be taken by U.S. Postal officials Tuesday morning.

Marcia.Ehlers@whiotv.com