UPDATE: The Western Highway is now open.

Almost 10 tankers were called out to the blaze near St Helens Plains on Sunday morning.

The highway was closed for several hours before police were able to reopen one lane.

EARLIER: The Western Highway is closed in both directions following a truck fire on Sunday, March 19.

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The state government's Department of Transport said traffic is closed in both directions following the incident near the intersection of Horsham-Wal Wal Road and the highway.

"Motorists should use Murtoa-Glenorchy Road to avoid the closure," a spokesperson said.

"The highway is likely to be closed for a number of hours as a clean-up operation continues.

"Motorists should use Murtoa-Glenorchy Road to avoid the closure. We ask that drivers take extra care when travelling on our road network, particularly in unfamiliar areas."

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Motorists are to be advised that Sawpit Swamp Road near Murtoa remains closed too.

The closure is under the control of Victoria Police.

To keep up to date with all road closures within Victoria, visit https://traffic.vicroads.vic.gov.au.