The London City Airport was shut down on Sunday night after an unexploded World War II bomb was found in the Thames river at the George V Dock, the Metropolitan Police and airport authorities said.

The ordnance was discovered during planned development work at the airport. The Royal Navy and the police are working on removing it, and authorities have asked people to steer clear of the airport on Monday.

Some flights in and out of the airport will be affected.

“At 10 pm, an operational decision was made with the Royal Navy to implement a 214-metre exclusion zone to ensure that the ordnance can be safely dealt with whilst limiting any risk to the public,” the BBC quoted an airport spokesperson as saying.