Firefighters had to pull back from an inferno after a barn roof collapsed scattering asbestos into the flames.
The collapse also put the huge building at risk of collapse, bringing further danger.
A mountain of straw bales caused a fierce blaze in a barn on the farm in the grounds of historic Temple Newsam house in East Leeds.
The fire started on Sunday but firefighters were still at the scene today.
Crews from nine West Yorkshire fire stations have been involved in tackling the blaze - Gipton, Stanks, Garforth, Batley, Leeds, Hunslet, Elland, Rawdon and Cookridge.
A spokesman for Leeds City Council said: "The fire is under control but is still active and West Yorkshire Fire and Rescue Service remain at the scene.
"Part of the roof structure of the barn did contain some asbestos which has been assessed and is of low-risk grade, and all parties involved are proceeding with the necessary caution to reduce the impact of the damage in order for the clean-up operation to begin as soon possible.
The farm remains closed to the public."
A spokeswoman for West Yorkshire Fire Service said the fire caused the barn roof to collapse into the flames.
"The majority of the roof was not asbestos but there was asbestos cement which contaminated the straw," she said. "In addition the site is structurally unsafe. So the firefighters could not go in to put the fire out because of the asbestos and because the building is unsafe."
Asbestos causes the deadly lung cancer mesothelioma for which there is no cure. In Leeds many victims died who had worked at, or lived near,
the JW Roberts asbestos factory at Armley.
The fire service spokeswoman said: "Structural engineers have to make the building safe, then the asbestos contractors can go in and remove the asbestos.
"There are still some pockets of fire but we have a pump there now on stand-by to make sure it does not spread."
The fire is believed to have been started deliberately, possibly by young people playing in the area where rare breed cattle are kept.
An off-duty fire officer raised the alarm and summoned colleagues to the scene.