Detectives are investigating a large fire at Southbank on Thursday afternoon which engulfed two unoccupied factories on the corner of Clarendon and Haig streets.

While the exact cause of the blaze is yet to be determined, police are treating it as suspicious.

Clarendon Street remains closed between City Road and Whiteman Street this morning.

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One witness, Carlo, said there was black smoke “billowing in.”

“It’s an old building next to an apartment complex,” he told Heidi Murphy, filling in for Tom Elliott.

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Image: Nine