NEWARK — Authorities are not sure why a bomb — which investigators later determined was a dud — was left at a Jewish cemetery, where frightened visitors discovered it on Sunday.

The device was found at the B'nai Abramahm Cemetery by security personnel with the Jewish Federation of Greater Metrowest New Jersey, CEO Dov Ben-Shimon said in a Facebook post. The group was holding a visiting event at the cemetery that allows people to pay their respects between the high holidays of Rosh Hashanah and Yom Kippur.

Only a handful of people were in the area where the device was found, according to Mark Gordon, the federation's spokesman. The device was seen on a tombstone, Gordon said. In Jewish tradition, small stones are placed on top of tombstones as a sign of respect, which is why the larger device likely stood out.

Ben-Shimon's post described the device as being made of "non-military firework mortar taped to a container of commercial lubricant." Gordon told New Jersey 101.5 that they were told by the Essex County bomb squad, which responded to the scene, that the device could not have exploded the way it was put together.

"They took it away and got rid of it, and within the hour everyone was back to their visiting," he said.

While vandalism at Jewish cemeteries is not uncommon, Gordon said he and Ben-Shimon agreed this was the first time they could recall something of this nature happening. He also said they were told that when something like this happens there is usually a message of some sort that goes with it. There was no such message seen in this instance. Because of that, he said they don't know what the intent was behind it, and are waiting for authorities to finish their investigation.

"This was not a big attended event. It was not publicized to a large degree," he said. "If someone was looking to have an effect, this clearly was not the event to do it at."

The B'nai Abraham cemetery can trace its roots in the city back to the 1800s, according to the congregation's website. Gordon said just last week the board agreed to increase security at the cemetery, including new fencing to help better protect the property.

Vandalism was reported last month at Congregation Agudath Achim cemetery in Freehold Township. Police reported that on Aug. 26 four headstones were knocked over.

Gordon said at this point he would be "hard pressed" to say that there was any connection between the two incidents.

The Essex county Prosecutor's Office directed all questions to the Newark Police Department. A spokesperson for the department said they would look into it for additional comment.