A two men found the backpack on top of and picked it up about 8:30 p.m. Sunday. When they opened it, they saw pipe bombs and wires and dropped the pack and ran to alert police, Elizabeth Mayor Christian Bollwage said

A police bomb disposal robot accidentally detonated a backpack full of pipe bombs that was found at a train station in Elizabeth, New Jersey early Monday, the FBI confirms – the third explosion in the New York area since Saturday morning.

Two men found the backpack in a trash bin and picked it up about 8:30 p.m. Sunday. When they opened it, they saw pipe bombs and wires and dropped the pack and ran to alert police, Elizabeth Mayor Christian Bollwage told CBS News.

Get push notifications with news, features and more.

About 12:30 a.m. Monday, a police bomb disposal robot cutting into the backpack accidentally detonated one of the five improvised explosive devices inside, Bollwage told reporters, according to NBC News.

The FBI field office in Newark confirmed on Twitter that no one was injured in the detonation.

CBS New York reports that heavily-armed FBI and ATF agents have raided a business in Elizabeth not far from the train station. It is unknown whether the raid is connected to the bomb investigation.

• Want to keep up with the latest crime coverage? Click here to get breaking crime news, ongoing trial coverage and details of intriguing unsolved cases in the True Crime Newsletter.

The explosion in Elizabeth, about 20 miles from Manhattan, is the third since Saturday morning.

The first explosion occurred about 9:30 a.m. Saturday at a U.S. Marine charity race in Seaside Park, New Jersey, about 85 miles from New York. No one was injured, but race organizers say that casualties could have been severe – but by a stroke of luck the 9 a.m. race start was delayed because of late registrations. Some 5,000 runners would have been passing by the bomb at the time of the blast had the race started on time, organizers said.

Then, about 8:30 p.m. on Saturday, a pressure-cooker bomb detonated near a garbage dumpster in the heavily-populated Chelsea neighborhood of Manhattan in New York City. Twenty nine people were injured, though only one seriously.

A second device, which did not go off, was found a few blocks away.

Authorities have not said whether the three explosions are linked and are continuing to investigate.

Five people were detained on Sunday night in connection with the Chelsea bomb blast after a traffic stop at the Verrazano-Narrows Bridge between Brooklyn and Staten Island in New York City, police sources told PIX 11 and other local news outlets.

The FBI office in New York confirmed the traffic stop, but said no one has been charged with a crime.