The Country Fire Authority confirmed a blaze which broke out at Durham Point, on the north side of the lake, about 4.20am yesterday was suspicious.

The fire burnt about a square kilometre of mainly fairy grass and reeds before it was brought under control about 8am.

Fighting the fire was difficult because of a lack of access for heavy fire trucks.

However, fire fighters were able to walk fire hoses out to the centre.

Some lighter all-terrain vehicles were able to move onto the lake.

During the early morning fire, residents as far away as Sebastopol called in to report the smell of smoke on a total fire ban day.

Despite the fumes and flames, joggers, walkers and cyclists were still out in force from around 6am.

Some interrupted their exercise routines to take photos and video footage of the action.

Wendouree Pde was closed to traffic between Forest and Burnbank streets for several hours while the fire was put out.

The CFA spent all day yesterday carrying out blacking works on the lake, with drifting smoke blanketing much of Ballarat, fanned by 20kmh north-westerly winds.

A CFA spokesman said yesterday police will be brought in to investigate the cause.

The spokesman said the fire could continue to smoulder in the lake bed for several days, with smoke also expected to be present for some time.

Yesterday's blaze follows a similar fire on the lake on December 30 last year, which burnt eight hectares of fairy grass and reeds.

After an investigation, it was determined Ballarat City Council staff had sparked the fire, which began about 100 metres from the northern shore, near Forest St.

It took three hours to bring under control.