He said he had marked the item as recovered because he had a similar item, which had not been used, in his bag.
Reid, who says he has worked in security since 1985 having previously served in the armed forces, added: “The lessons learned will be ‘how was that not found?’
“What are the implications for anybody at sporting events? How do they check those areas?
“I made a mistake, a devastating mistake.”
Why was the device not detected earlier?
A routine sweep of the ground by sniffer dogs on match day would not have detected the device as it did not include explosives, and it was actually discovered by a member of the public.
After it was found on what should have been the final day of the Premier League season, Greater Manchester Police ordered the evacuation of the Sir Alex Ferguson Stand and the Stretford End, before it was subsequently announced the fixture had been abandoned.
“Once a live situation was identified, the club and police had no option but to treat the matter as a potential terror threat,” said Woodward.
Questions for Manchester United
The Premier League has praised the way the incident was dealt with.
Greater Manchester Police, who worked closely with a bomb disposal team on Sunday, said although the device was not “a viable explosive”, in appearance it “was as real as could be”.
Kate Green, Labour MP for Stretford and Urmston, has written to Woodward stating it is “particularly troubling” the device went undetected.
She added there is “considerable concern” about the performance of the private security firm involved and wants United to reassure the public on safety issues at Old Trafford.
Green also wants United to outline how they will compensate fans for expenses, including travel and accommodation costs.
The £3m evacuation
United will refund all tickets and allow ticket holders from both clubs to watch Tuesday’s rearranged game for free, while United season ticket holders will be given a credit.
It is a gesture that is estimated will cost United about £3m.
Woodward stressed United and the police “would ensure that robust security measures continue to be of the highest priority” for the rearranged game.
Bournemouth are offering free coach travel for supporters with a valid match ticket.
Chairman Jeff Mostyn told BBC South Today: “They make sacrifices every single week and go to great expense travelling away.”