A suspicious item that forced the evacuation of Manchester United's Old Trafford stadium on Sunday was later identified as a training device left behind by a private company, police said.
The Premier League match between United and Bournemouth was postponed after the item was discovered just prior to kick-off.
After conducting a controlled explosion at the stadium, officials said the item was a training device that had accidentally been left by the private company following the training exercise.
The exercise involved search dogs trained to seek out explosives, Greater Manchester Police said in a statement late Sunday night.
“Whilst this item did not turn out to be a viable explosive, 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," the statement said.
The season-ending match will now be played Tuesday, the Premier League said.
A public address announcement about 30 minutes before kick-off told fans in the Stretford End and Sir Alex Ferguson Stands to leave the stadium, while the players were taken off the pitch during their warm-ups.
Supporters in the Sir Bobby Charlton and East stands were told to remain calm and stay in their seats.
Television pictures showed police with sniffer dogs walking through the stands before the abandonment was announced shortly after and the stadium was evacuated.
"The safety of fans is always our highest priority," said Ed Woodward, United's executive vice chairman.
"The club takes security very seriously and staff are regularly trained with the police and emergency services to identify and deal with these incidents.
Woodward said the incident would be investigated.
The rearranged match could have been important for United's Champions League hopes, but fourth-placed Manchester City drew 1-1 at Swansea earlier Sunday, meaning United need to win by 19 goals to make up a three-point deficit and crucially a far inferior goal difference.
United are sixth behind Southampton on goal difference and are set to play in the Europa League instead. They also face Crystal Palace in the FA Cup final on Saturday.