The Northern Ireland Fire & Rescue Service (NIFRS) believe that a blaze on the site of the former Convent of Mercy in Stream Street, Downpatrick was deliberately started.

NIFRS were called to attend the fire just after 19:00 BST. At the height of the incident 70 firefighters were involved.

Crews used breathing apparatus, firefighting jets and two aerial ladder jets to tackle the fire.

Police also attended to help with traffic management and said the scene was being held as investigations continue into the cause.

The building is attached to St Patrick's Church in the town.

NIFRS said all firefighting operations had concluded by 07:00 on Monday.

A total of 10 appliances attended, supported by two aerial ladder appliances, a Command Support Unit and a water tanker.

SDLP councillor Conor Galbraith who was at the scene said: "It doesn't look like it could spread, with most of the fire located on the building's roof, which appears to be caved in"

A priest had been ordained there on Sunday afternoon, "just hours before the blaze," he said.

He added that it was sad to see the fire in "such a historical part of our town".

Galbraith's party colleague, Colin McGrath, described the blaze as "difficult to watch".

"Many local people will have memories of the convent and the role it played over the years."

The South Down MLA said the building "remained a familiar part of the Downpatrick skyline".

"Seeing it go up in flames is upsetting," he added.

Sinn Féin councillor Oonagh Hanlon appealed to the Downpatrick community to avoid the area around the old convent site.

"I hope everyone involved is safe and well, and our thoughts are with anyone affected by this incident," she said.

Police and NIFRS have also asked members of the public to keep away from the area.