Warrnambool police are continuing to seek information from a resident of a housing unit that was partially destroyed by fire on Wednesday night.

Detective Senior Constable Wayne Ryan, of the Warrnambool police crime investigation unit, said a Victoria Police arson chemist attended the Ocean Grove home in Warrnambool on Thursday afternoon.

He said it was undetermined how the fire started, but it began in the living room, which led to flames roaring out the front window.

"We can't say if the cause of the fire is suspicious or not, it's undetermined at this stage," he said.

"It's an ongoing investigation.

"The female resident is currently in police custody on other matters. We are continuing to make enquiries with her," he said.

Anyone with information about the fire is requested to contact Crime Stoppers on 1800 333 000.

Thursday: A Victoria Police arson chemist is on the way from Melbourne to assess the cause of a house fire at Warrnambool's Ocean Grove.

Warrnambool police Sergeant Stuart Revell said neighbours raised the alarm soon after 8pm on Wednesday evening.

"Neighbours contacted Triple Zero (000) about 8.30pm and police and the Warrnambool fire brigade (Fire Rescue Victoria) attended," he said.

"No one was home and no one was injured. The cause of the fire is unknown at this stage and an arson chemist is coming from Melbourne to assess the situation."

The damage is extensive. The brick unit is part of a multi-dwelling building.

Neighbour Penny Simons said the resident had been at home during the day and socialising, but had left the property before the fire started.

An FRV spokesperson said Warrnambool firefighters attended.

"FRV and CFA (Country Fire Authority) crews responded to a building fire in Warrnambool on Wednesday night after a caller to 000 reported the fire at 8.12pm," she said.

"Firefighters arrived to the Ocean Grove scene to find a brick house fully alight.

"Wearing breathing apparatus, firefighters worked to attack the fire and prevent it from spreading.

"The fire was brought under control at 8:23pm, with crews remaining on scene for some time to monitor for hot spots and ventilate the facility.

"Ambulance Victoria attended for firefighter welfare. At this stage the fire is being treated as suspicious, and the incident has been handed over to Victoria Police," she said.

Warrnambool police crime investigation unit Detective Senior Constable Wayne Ryan said the cause of the fire was being treated as suspicious at this stage.

He said the arson chemist was expected to determine a point of origin of the fire which would guide investigators.

Anyone with any information is requested to contact Crime Stoppers on 1800 333 000.

There were also fires near South Purrumbete yesterday and Glenormiston North.

Late Wednesday night the Country Fire Authority said the grass fires at Glenormiston North and Beals Road, Tandarook, were under control.

Smoke was visible from both during the late afternoon and evening and firefighters continued to monitor the situation overnight.

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