The game between Manchester United and Bournemouth was abandoned
The mayor of Greater Manchester has led calls for a full inquiry after it emerged on Sunday night that a fake bomb that sparked an evacuation of Old Trafford was a training device left by a private company.
Tony Lloyd, who is also the city's police and crime commissioner, said the false alarm was a "fiasco," which had endangered supporters.
Police said an "incredibly lifelike" device - which caused the club's final Premier League game of the season to be abandoned - had been used in a training exercise involving explosive search dogs. "It is outrageous this situation arose and a full inquiry is required to urgently find out how this happened, why it happened and who will be held accountable", Lloyd added.
"This fiasco caused massive inconvenience to supporters who had come from far and wide to watch the match, wasted the time of huge numbers of police officers and the army's bomb squad, and unnecessarily put people in danger, as evacuating tens of thousands of people from a football stadium is not without risk."
"Whilst this in no way demeans the professionalism of the police and stewards responsible for getting the fans out, or the supporters' calmness and cooperation during the evacuation, it is unacceptable that it happened in the first place."
Reports of a suspect package at Old Trafford prompted the evacuation of the Stretford End and Alex Ferguson Stand around 20 minutes before the 3pm kick-off. Those remaining in the 75,000-seater stadium were told the game against AFC Bournemouth was off shortly after 3.15pm.
A controlled explosion was carried out but Greater Manchester Police (GMP) later confirmed the device - found in the ground's North West Quadrant - was not viable. It is thought to have consisted of a mobile phone attached to a pipe or canister.
Bomb disposal experts carried out controlled explosion at Old Trafford on what is described as incredibly lifelike explosive device...— G M Police (@gmpolice) May 15, 2016
Assistant Chief Constable John O'Hare from Greater Manchester Police said; "Following today's controlled explosion, we have since found out that the item was a training device which had accidentally been left by a private company following a training exercise involving explosive search dogs."
"Whilst this item did not turn out to be a viable explosive, on appearance this device was as real as could be, and the decision to evacuate the stadium was the right thing to do, until we could be sure that people were not at risk."
Ed Woodward, Manchester United's vice-chairman, said the club will "investigate the incident to inform future actions and decisions". He added; "The safety of fans is always our highest priority."
Suspicious item found at Old Trafford today, which required controlled explosion, was a training device https://t.co/55n06zNwU3— G M Police (@gmpolice) May 15, 2016
"I'd like to thank the support from the police which was first class and the impeccable response from fans of both teams. The club takes security very seriously and staff are regularly trained with the police and emergency services to identify and deal with these incidents."
It is understood that both sets of players were kept in the dressing rooms for around 40 minutes before being taken to a suite, being looked after by security and hospitality staff. The game was called off after discussions between the Football Association, the Premier League and police. The abandoned game has been rescheduled for Tuesday at 8pm, with fans offered refunds for their Sunday ticket, as well as free entry for the rearranged fixture.