Five suspected explosive devices have been found in a backpack near a train station in New Jersey as the security alert gripping America ratcheted up in the wake of the Manhattan bombing.

One of the devices exploded when a bomb squad robot tried to disarm it near Elizabeth train station, Associated Press reported the local mayor as saying.

Christian Bollwage said that the device exploded shortly after 12:30am on Monday. The FBI was leading the investigation and working to disarm the other four devices. Continue reading.