Manchester United's executive vice-chairman Ed Woodward has said the fake bomb found at Old Trafford on Sunday could not have been detected by sniffer dogs.
Woodward also said the device had earlier been signed off as having been removed by the company that had planted it during a security training exercise.
Police and security staff evacuated the stadium shortly before United's game at home to Bournemouth was due to kick off on Sunday, and the match was abandoned as a controlled explosion was carried out.
It later emerged that the device had been placed in the stadium as part of a training exercise for dog handlers at Old Trafford and was left at the ground afterwards in error.
The club's executive vice-chairman Ed Woodward has released a statement regarding the match v Bournemouth: https://t.co/6bchdIefuW #mufc
- Manchester United (@ManUtd) May 16, 2016
In a statement, Woodward said the company, Security Search Management and Solutions Ltd, had "left [the device] in error following the training of dog handlers" and "signed the device as having been recovered along with the 13 other devices at the end of the exercise."
He also stressed that the device "could not have been detected by sniffer dogs on the routine matchday search of the 100 Club, as it contained no explosives and was used in an exercise training handlers not dogs."
He emphasised that he was "proud of how our staff responded" and said that both United and Bournemouth fans "behaved impeccably," adding: "The evacuation -- the first of its type in the UK -- was a complete success."
Christopher Reid, director of the security company responsible for leaving the device, told the Daily Telegraph he does not believe it was necessary to evacuate the stadium.
Chris Reid holds up a replica bomb similar to the one that caused the full scale evacuation of #OldTrafford ytdy. pic.twitter.com/G3BCVzP2g6
- Jim Old (@SkyFixerJim) May 16, 2016
However, Woodward said: "Once a live situation was identified, the club and police had no option but to treat the matter as a potential terror threat; we could not have assumed it was a training exercise error. Presented with the same situation in the future, we would take the same action.
"We have worked very closely with the police and counter-terrorism specialists for many years now and enjoy their support on a daily basis.
"For tomorrow's [Tuesday's] rearranged match against Bournemouth, we are working closely with Greater Manchester Police to ensure that robust security measures continue to be of the highest priority.
"We are conducting a detailed evaluation with the help of the police and will share our findings across the rest of the game. Valuable lessons will have been learned from yesterday's events and it is important that those are shared with other stadium operators to ensure that the safety of the public remains the first duty of us all."