Police are investigating a Murray Bridge house fire they say was deliberately lit.

Emergency services were called to an abandoned property on Railway Terrace around 5.30pm on Monday.

Metropolitan Fire Service and Country Fire Service personnel wearing breathing apparatus did not take long to put out the flames, but the building was extensively damaged.

At one point firefighters feared its roof might collapse.

Police closed the street to traffic while emergency services remained at the scene.

Fire cause investigators later determined that the blaze had not been an accident.

A bystander told Murray Bridge News a couple of people had been seen running from the scene.

Anyone with information about the fire's cause should contact Crime Stoppers on 1800 333 000 or at www.crimestopperssa.com.au.

You can remain anonymous.

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