Police in Northern Ireland have been criticized for their handling of a security alert in Newry last weekend which led to the discovery of a 500lb bomb. Hundreds of motorists drove past the van containing the bomb after someone removed traffic cones cordoning off the area. Defending the police's actions, Chief Superintendent Alasdair Robinson said a full cordon had been put in place when the suspect vehicle was located. "The warning came in to a local charity and it said the following: 'This is the IRA, there is a bomb under the underpass,'" he said. "No location was given and there was nine seconds of recording. The previous one, the first one said: 'This is the IRA, we've planted a bomb on the underpass at the Berliss Road and it is to go off in 45 minutes.' Now there is no Berliss Road on the M1. The M1 goes from Belfast to the west. "The M1 of course, is the A1/M1 which is the national north south route, so that was the level of ambiguity." Robinson said police did not at that stage know where the bomb was. "It wasn't until almost an hour later that we could confirm that we had a suspect vehicle. At that point, we put a full cordon in place," he added. "We closed the roads, both with police and the Roads Service, who kindly helped us with that. We had the whole scene completely secure and locked down for the evening." He said some members of the public had "breached" the police cordon. "You can't blame all of the people who drove past because they came to what they thought was an open road," he said. "We checked the cordon and we put police back in to close them down." He added that the PSNI would review its use of signage. "It is not part of anyone's plan to allow any member of the public to go anywhere near what was a suspect device. Police believe that the van containing the bomb was abandoned in the underpass because of increased police activity in the wake of the Constable Ronan Kerr murder. Several controlled explosions on the vehicle were carried out.