Manchester - A fake bomb inside Old Trafford that forced the abandonment of Manchester United's last Premier League game of the season triggered angry calls on Monday for action as the club faced a multi-million pound bill for the "fiasco".
As inquiries started into the incident which led to bomb disposal experts blowing up a mobile phone attached to a gas pipe, United vowed to reimburse the tickets of 75 000 fans who were evacuated Sunday ahead of the game against Bournemouth.
They will also give them free entry to Tuesday's rearranged match against the south-coast side. That gesture alone could cost United more than $4.3 million.
Tony Lloyd, Manchester's mayor and police and crime commissioner, said: "It is outrageous this situation arose.
"A full inquiry is required to urgently find out how this happened, why it happened and who will be held accountable.
"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."
Officials said a company which conducted a security exercise at Old Trafford had left the fake bomb - a mobile phone attached to a gas pipe -- in a stadium toilet.
The device was found just before Sunday's kick-off and the evacuation ordered.
Army experts staged a "controlled explosion" before police announced that the suspect device was "incredibly lifelike" but "wasn't viable."
Greater Manchester police assistant chief constable John O'Hare said: "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."
United's vice-chairman Ed Woodward said an investigation would be launched to guide "future actions and decisions."
British media named the company that left the device in the stadium as Security Search Management and Solutions.
They said the firm had staged a training exercise for sniffer dogs at Old Trafford but left the fake bomb behind.
Christopher Reid, owner of Security Search Management, told the Daily Mail his company was "getting the blame" for the fake bomb but refused to make any comment until after he had spoken with Manchester United.
The incident left a number of spectators deeply disappointed.
About 3 500 Bournemouth fans made a 800km 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."
Sam Stride, a United supporter from Bristol, said: "Unbelievable. This is the first time I have been to Old Trafford to see a game. My mate and I have known each other for 63 years and we travelled up from Bristol together. We sat in the Stretford End for about five seconds before they asked us to leave. It's very disappointing."
Sunday's incident was United's second security scare of the week after their team bus was attacked by West Ham United fans on Tuesday.
The Manchester United Supporters Trust said it had raised the 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 Africa fan, named only as Moses.
Players from the two teams were already on the pitch when the game was cancelled and were quickly led back to the dressing 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," Mata said.
"There's been nerves and tension," United midfielder Ander Herrera told Spanish radio of the evacuation.