The package – contained in an unmarked brown shoe box – was discovered by chance in a shelter on Princes Street Gardens by a shocked park

ranger.

Detectives remained tight lipped about the contents of the box, but the Evening News understands it included “wires and a battery” and was left on the ground.

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That was enough for police to engage emergency protocols and seal off the area while they called in army bomb disposal experts from Craigiehall. A team of explosives experts carried out a controlled detonation on the package at around 8.10pm on Thursday – around three hours after the alarm was first raised.

A “Gold” meeting of senior commanders decided to extend the parameters of the investigation and call in specialist support to conduct a sweep of the area and trawl CCTV for the identity of whoever left the package.

Scottish Government ministers last night said they had been briefed on the situation.

“We’re looking into all possibilities and not ruling anything out, said chief inspector Alan Carson, “We’re keeping an open mind and it’s early stages.

“We know it wasn’t a viable device. It could’ve been a hoax. It could’ve been someone who left it behind carelessly.”

He added: “It may have been something made to look like a bomb or it may have been left completely innocently – entirely by accident.”

He revealed there was no note and no phone call to emergency services, and it was only found on the north side of the gardens during a routine patrol by the ranger who opened it before calling police.

Members of the public were in the grounds at the time, but no evacuation was carried out.

An MoD spokesman confirmed it was a team from the 30-strong 521 Squadron of the 11 Explosive Ordinance Regiment at Craigiehall who dealt with the package.

They moved the contents towards King’s Stables Road where they were destroyed.

Officers are checking CCTV and all police closures put in place following the discovery of the package have been lifted.

“It’s such a complex area to search because of the terrain and the environment,” said CI Carson. “We need to search the area thoroughly for anything suspicious or of concern or that leads us to identify who left the item. The package discovered was a brown, shoe-sized box,” said CI Carson. “I can’t go into details in terms of the contents but they looked out of place.”

Police insisted the item posed no danger but said officers are treating the incident with “the utmost seriousness” in the current security climate.

Officers are not treating the find as terror-related and no intelligence exists of a specific threat to the Capital – though the UK alert remains “severe”.

CI Carson praised the park ranger’s vigilance and asked the public to be “alert but not alarmed”.

A council spokesman said: “We continue to support Police Scotland with their investigations.”