a KEY route in Scotland's capital was locked down due to a major chemical incident after a man and woman took part in a cyanide suicide pact in a luxury hotel.

Experts wearing chemical suits from the government's emergency crisis team, Scottish Resilience, rushed to the five-star Scotsman Hotel on the North Bridge in Edinburgh after staff found the man and woman lying in a sixth floor bedroom at 12.15pm yesterday.

Surrounding streets were roped off amid initial fears of a terrorist attack and the public was warned to stay away from the immediate area. The city was thronged with tourists as it geared up for the start of the festivals.

Firefighters clad in the ­protective outfits entered the room after the workers raised the alert and emerged with items secured in air-tight containers.

Police would not say whether the guests left a suicide note, but it is believed the couple were found in bed with an opened container, which is being investigated.

The sixth floor was evacuated, but hundreds more guests were allowed to remain on the premises after the all-clear was given.

Guests said they woke up to a horrible smell.

Ann Lewis, 48 said: "When we went down for breakfast just after nine we smelled something really horrible. It almost smelt like sewage."

The bodies of the victims, who have not yet been named, remained in the hotel throughout the day while investigations went on.

There was confusion on the street outside the hotel for several hours about the situation as ­emergency services remained at the site.

One of the lanes of the North Bridge was cordoned off and about 20 emergency services vehicles lined the route.

Police Scotland east division had a dozen vehicles on the site at one stage, and the Scottish ­Ambulance Service and Scottish Fire and Rescue Services both set up command centres on the thoroughfare. Officers were put on guard at staff exits.

A police source said: "Whether or not this chemical has been digested or absorbed we don't know yet."

The Scotsman hotel, one of the city's most notable buildings which commands views towards Princes Street, is situated off the historic Royal Mile.

It is currently experiencing one of its busiest periods of the year as the busy summer season is under way. Thousands of performers and tourists are flocking to ­Scotland's capital for the festivals.

Police, fire and ambulance crews were sent to the scene, while the road remained largely open to traffic.

Norma and Derek Cameron, from Kelso in the Borders, are staying at the hotel for two nights while they attend the Royal Edinburgh Military Tattoo.

They were prevented from returning to their room on the eighth floor.

Mrs Cameron, 71, said they were just preparing to go to the Military Tattoo at Edinburgh Castle.

She said: "We wanted to get in and get refreshed.

"The police weren't giving anything away. They just said that the hotel had been closed and everyone evacuated.

"It's horrible to think about. I'm not sure I want to go back in now."

Lynn Massie, 34, and Neil Cooper, 31, from Aberdeen, were staying at the Scotsman and were waiting to collect their luggage after a two-day break.

Ms Massie said: "We're really shocked. I feel very sorry for the families of the two people.

"I don't know what happened but it's quite sad.

"You don't expect something like this to happen at a five-star hotel. It's a shame for the hotel staff too."

Last night things began to return to normal as fire crews left the scene at about 4pm, shortly before rush hour.