Faced with a backlog of patients, a Halifax emergency room triggered a special alert usually reserved for incidents with mass casualties Tuesday morning.

The QEII Health Sciences Centre declared a "code orange" for about an hour, as patients lined the corridors and others waited outside in ambulances because of a lack of suitable hospital beds.

An unusual increase in the number of patients has swamped emergency rooms in the Halifax area in the last 48 hours.

Peter Graham, spokesman for the Capital District Health Authority, said the load is particularly heavy at the Halifax Infirmary, where some people have been waiting 24 hours to be admitted to another section of the hospital.

"Patients who don't have a bed in the hospital are still treated in the emergency department," Graham told CBC News Tuesday.

"They are in a bed either within one of the assigned bays within the hospital or in some instances in the corridors within the emergency department, which we use when we are at or over capacity."

The hospital declared a mass casualty alert around 8 a.m. when emergency physicians couldn't find specialized beds for 16 patients.

Dr. John Ross, head of emergency medicine, triggered the "code orange," which is usually used to deal with major industrial or vehicle accidents. It was used during the SwissAir disaster in 1998 and in 2004 when an MK Airlines plane crashed.

Ross said the code orange is an internal hospital response, not an alert intended to frighten patients.

"It is intended to focus on the task and get them all talking to each other and get them saying, 'If you are doing other things that aren't as important, then drop those and try to find some spaces within the hospital'," said Ross.

By mid-morning, there were 19 people in the hospital and three outside in ambulances waiting for beds. A flat-screen monitor in the hospital declared that for walk-in patients, it could take six hours and 42 minutes to see a physician for the first time.

Ross said sending patients to other hospitals isn't an option since they are facing a similar bed crunch.

One possible solution, he said, is to send some patients back to regional hospitals once their treatments in Halifax are done.

Graham said there is no one cause for the large number of patients.

The icy conditions have led to traffic accidents and slips and falls, but Graham said there are also people coming in with a variety of ailments.

"We've just been seeing a lot of very sick patients," he said.

Graham said by 3 p.m., beds were found for all 16 patients who had been waiting more than a day.

With files from the Canadian Press