Firefighters battled a large blaze at the old Royal Victoria Hospital on Monday afternoon.
The Scottish Fire and Rescue Service was called to the scene at around 4.15pm.
A total of nine crews are currently tackling the blaze, which has taken hold in a disused building.
The hospital was shut in 2012 when a new unit opened at the Western General Hospital nearby.
Thick black smoke could be seen billowing from the scene, with firefighters using a platform to hose down the flames from above.
A police presence was also in place on Craigleith Road to guide drivers past the site’s entrance.
Dozens of onlookers gathered nearby to watch the incident unfold, with one local resident saying their water supply had been shut off while the firefighters got to work.
One local resident, who did not want to be named, said he could see the blaze from his house.
He said: “It’s a huge amount of smoke and clearly it’s not out yet.
“It looks quite violent - it’s very black smoke.”
It is not yet known if anyone was hurt.
A Scottish Fire and Rescue Service spokesman said: “Crews were called this afternoon to a fire in a derelict former hospital building.
“It has been upgraded to a level three incident with nine crews and pumping appliances in attendance.
“The incident is ongoing.”
A thick plume of smoke could still be seen billowing from the site at 9am this morning, 23 May.