Lismore Police were first to arrive at the scene of a fire which engulfed a Dawson Street, Lismore, premises at 1.30am on Monday morning.
All residents from the three units escaped with no injuries.
The fire has also damaged both adjoining premises, with the eastern side roof on one premises collapsing.
The other business premises suffered minor smoke damage.
Lismore detectives are seeking any witnesses or information to the fire which they are treating as highly suspicious.
The premises, an older wooden dwelling, has suffered major damage.
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Highway Patrol Police last week conducted operation Speed Week which has netted numerous motorists for speeding offences; the volume of the results has raised concern with Police.
A motorist was detected travelling at 109 kph in a 60kph zone in Lismore Heights, and 25 infringements have been issued at the Goonellabah School zone on one day.
Police detected 952 speed camera-detected infringements, with the majority of these issued on the Bruxner Highway in Lismore, travelling in both directions.
Issued during the week were 166 other speeding infringements, 4 seat belt infringements, 3 unregistered vehicles were detected and one unlicensed driver was arrested.
Motorists are warned Highway Patrol will continue to target these areas following these startling results.
Motorists are reminded to drive to the sign posted speed limit.