The blaze started in the rear shed and pergola area of the Anderson Street home in Wodonga about 9.40am yesterday.

Thick black smoke could be seen pouring from the back of the property from a lengthy distance.

Multiple people made Triple-0 calls after spotting the smoke.

CFA fire investigators and detectives attended the scene and are investigating the cause of the blaze.

Wodonga senior station officer Sean Crosthwaite said it took about 25 minutes to bring the incident under control.

There had been concerns the fire would spread into the house.

"We received a call to a structural fire," he said.

"Upon arrival we found the shed in the rear and pergola area to be well alight in terms of fire.

"There's significant damage to the shed and pergola of the house."

The teenager had been inside the property when the blaze started.

He fled when the fire took hold and raised the alarm with nearby resident, and about 15 firefighters in three trucks attended the property.

Police spoke to the boy - who appeared to be distressed - at the scene.

The fire gutted the shed and destroyed everything inside.

Items under the pergola were also damaged.

Bikes, lawnmowers, gardening tools and gym equipment was burnt.

A car was removed from the property before firefighters arrived.

A large number of bystanders watched as firefighters battled the blaze.

The smoke set off an alarm at the adjoining Toyota dealership over the back fence of the home, but the business was undamaged.

A solar system was attached to the roof, which had to be isolated by firefighters before they could tackle the blaze.

Firefighters also searched the home to make sure no-one else was inside.

Mr Crosthwaite said the flames came close to the brick home.

"It encroached into the rear pergola," he said.

"It was only metres from entering the actual house as such.

"(The teenager) did the right thing and exited the house straight away.

"He went into the care of neighbours."