A suspicious package which prompted the evacuation of Manchester United's stadium the morning before it was subject to a controlled explosion has been identified as a training device, police said.
The discovery of the device, earlier described by police as "incredibly lifelike" but not viable, forced the club's Premier League match against Bournemouth to be abandoned.
"Following today's controlled explosion, we have since found out that the item was a training device which had accidentally been left by a private company following a training exercise involving explosive search dogs," Assistant Chief Constable John O'Hare of the Greater Manchester Police said in a statement.
"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."
Two of the Old Trafford stands were evacuated about 20 minutes before the scheduled kick-off on discovery of the suspicious package. Soon after, the game was called off and the whole 75,000-seater stadium cleared.
Police investigated the package and used sniffer dogs to search the area, before calling in an army bomb disposal unit. TV footage showed fire engines arriving at the stadium.
"Bomb disposal experts carried out controlled explosion at Old Trafford on what is described as incredibly lifelike explosive device," Greater Manchester Police said later on Twitter.
"Full assessment now concluded and found device wasn't viable. A full search of the stadium is ongoing."
On Wednesday Britain raised the threat level from dissident Northern Ireland militants to "substantial," meaning an attack on the British mainland is considered a strong possibility.
Manchester United said in a statement on its website the package had been found in the North West Quadrant, and the match abandoned on police advice.
"We don't make these decisions lightly and we have done this today to ensure the safety of all those attending," Assistant Chief Constable John O'Hare said in a statement.
United cannot qualify for next season's Champions League, after Manchester City drew at Swansea City on Sunday. They are sixth in the Premier League table and would move above Southampton into fifth with a draw or victory against Bournemouth.
They play Crystal Palace in the FA Cup final on this weekend and it is not clear when a rescheduled game against Bournemouth, its final Premier League match of the season, will be played.
In a statement posted on Twitter, the Premier League said it would seek to rearrange the fixture "as soon as practically possible".
"When it comes to matters of security it is obviously right that Manchester United and the Premier League place the safety of supporters and employees foremost," it said.
"It is always the last resort to abandon one of our fixtures."
