CNN  — 

The security firm that left a mock pipe bomb inside Manchester United’s Old Trafford stadium apologized for its role in the security mishap.

“I am absolutely devastated that a lapse in my working protocols has resulted in many people being disappointed, frightened and inconvenienced. Nothing I can say will rectify that,” said Chris Reid, the head of security at Security Search Management Company, in an emailed statement.

The company left behind an eight-inch, lifelike explosive device in the fifth floor of the men’s bathroom in the stadium. It had been used during a training session on Wednesday.

The discovery of the lifelike explosive device triggered a mass evacuation and the cancellation of a key soccer game Sunday between Manchester United and AFC Bournemouth.

Shortly before the 3 p.m. kickoff, Manchester United staff alerted police to the suspicious item found in the bathroom.

A police unit used a controlled explosion to destroy the mock bomb.

The incident infuriated a number of people, including the Greater Manchester Mayor and Police and Crime Commissioner Tony Lloyd, who described the incident as a “fiasco” and called for a full inquiry.

Lloyd said security exercises are important but said the latest incident was “incompetent.”

He had said in an earlier statement that he was particularly unhappy at the “waste of time of huge numbers of police officers and the army’s bomb squad.”

Reid briefly spoke to CNN on the phone from his home in England.

“Words cannot express what I feel,” he said. He called the incident inconvenient and unfortunate. This was an “honest mistake and I have to live with that,” Reid said.

Last week, the company conducted a safety training session where five dog handlers had to locate various training objects placed throughout the fifth floor of the stadium, he said in an emailed statement.

Reid said he mistakenly thought all the training devices had been collected after the session, because he had a similar mockup of a pipe bomb in his bag.

“This mistake is entirely mine and I have to take full responsibility for leaving the training item behind on Wednesday,” he said in the statement.

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Manchester United said the evacuation on Sunday was “a complete success.”

“The safety of the fans is our number one aim at every event we host at Old Trafford,” said Ed Woodward, the Manchester United executive vice-chairman. “Overall, I’m proud of how our staff responded.”

The match is rescheduled for Tuesday at 8 p.m., the Premier League said.

CNN’s Ashley Fantz, Christina Macfarlane, Aleks Klosok and Damien Ward contributed to this report.