The Glenelg Highway has reopened after police closed it to all traffic just before midday.

Smoke is still visible in the area.

A CFA spokesperson at the Warrnambool Incident Control Centre said there had been no asset loss or injuries from the fire 500 meters north of the highway in swampy land.

"It's under control - it's approximately 10 hectares of swampy country - the crews will be out there for some time," the spokesman said.

"It's approximately 2 kilometres west of the Hamilton Racecourse.

Temperatures topped 40 degrees in Hamilton shortly after noon.

The fire had been heading in a southerly direction.

Around 13 trucks responded to the blaze earlier this morning.

The cause of the fire remains uncertain.

"We're not sure at this stage. There is a fire investigation out there," the spokesman said.