Manchester - The head of a security firm on Monday accepted "full responsibility" for accidentally leaving behind a dummy bomb that caused Manchester United's Old Trafford stadium to be evacuated.
Chris Reid, managing director of Security Search Management and Solutions, said he was "devastated" by the blunder, which left United facing a multi-million-pound bill.
"This mistake is entirely mine," an emotional Reid told reporters outside his southeast London home. "I have to take full responsibility for leaving a training item behind on Wednesday."
The fake device, an imitation pipe bomb attached to a mobile phone, was discovered minutes before kick-off in United's final Premier League game of the season against Bournemouth on Sunday.
The stadium was promptly evacuated and the game called off before the device was safely detonated by bomb disposal experts. The teams will now meet on Tuesday.
Reid, a retired Scotland Yard police officer, said the device, which was labelled, had been left hanging from the back of a toilet cubicle door in the stadium's northwest quadrant.
He explained that after carrying out a training exercise for five dog handlers, he mistakenly thought that a similar device in his bag was the one he had left in the toilet.
"I am absolutely devastated that a lapse in my working protocols has resulted in many people being disappointed, frightened and inconvenienced," he added. "Nothing I can say will rectify that."
United vice-chairman Ed Woodward had earlier explained that the device was left in error by a sub contractor and mistakenly recorded as having been removed.
"The contractor had signed the device as having been recovered along with the 13 other devices at the end of the exercise," he said in a statement.
United vowed to reimburse the tickets of the 75,000 fans who were evacuated and give them free entry to Tuesday's rearranged match.
That gesture alone could cost the club more than three million pounds (3.8 million euros/$4.3 million).
Tony Lloyd, Manchester's mayor and police and crime commissioner, branded the situation "outrageous" and called for a "full inquiry".
"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," he said.
Following the controlled explosion, police announced that the suspect device was "incredibly lifelike" but "wasn't viable".
The incident left a number of spectators deeply disappointed.
About 3,500 Bournemouth fans made a 500-mile (800-kilometre) round trip to Manchester to see their club's first league game at Old Trafford.
Bournemouth manager Eddie Howe told the local Daily Echo newspaper: "It was a real anti-climax to a day everyone had been looking forward to.
"But all those disappointments and emotions really go out of the window when you think about the supporters and everything they have put into the day -- financial costs, time, effort."
Bournemouth have offered free coach travel for supporters travelling to the rearranged game.
Sunday's incident was United's second security scare of the week after their team bus was pelted with cans and bottles by West Ham United fans last Tuesday.
The Manchester United Supporters Trust said it had raised money for a fan who had travelled from Sierra Leone to see his first Old Trafford game to get a ticket for next Saturday's FA Cup final against Crystal Palace at Wembley.
The trust said it had rearranged flights and found hotels for the fan, named as Moses Momodukamara.
Players from the two teams were warming up on the pitch when the game was cancelled and were quickly led back to the changing rooms.
"What happened in Old Trafford this Sunday left all of us who were there absolutely shocked," United's Spanish midfielder Juan Mata wrote in a blog on the club website.
"It helped not to spread panic around, although all of us had a very odd feeling; something like strain mixed with a lack of understanding.
"I feel sorry for all those people who had to go back home without watching the game."
England manager Roy Hodgson said the calm and orderly nature of the evacuation had been reassuring.
"Although the bomb itself turned out not to be one, it's still good to see the authorities are really on the ball and doing their job," he said during a press conference on Monday.