Greater Manchester Police have confirmed they carried out an operation at the ground but were later able to confirm that the substance was non-toxic.

The Sun report that the package was addressed to Ferguson, who was not present at the time, having flown with the team to face AC Milan in the second leg of their Champions League semi-final tonight.

A GMP spokesman told the newspaper: "We were called to the training ground following reports of a suspicious package.

"The package was opened by a member of staff and an unidentified substance was discovered.

"Police and Fire Service officers attended the address as a part of a pre-planned operation," he added.

"Tests were carried out on the substance in an effort to establish its nature. Officers are also investigating the origins of the package and our inquiries are continuing.

"It could have been toxic - then we'd have been dealing with a very different situation. We are still investigating the origins of the package."

A Red Devils spokesman added: "It's just fortunate that the substance turned out not to be dangerous."