A serious truck crash has closed a major Sydney motorway sparking peak hour chaos for morning commuters.

NSW Transport said M7 westbound lanes have been closed after the crash involving two trucks just past Quakers Hill Pwy just before 6am on Wednesday.

Paramedics were treating both drivers for minor injuries, with traffic banked up for approximately 5km.

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Westbound traffic is being diverted off the M7 onto Quakers Hill Pwy and Richmond Rd to return to the motorway.

“Motorists in heavy vehicles are advised to exit the motorway at Sunnyholt Rd instead,” NSW Transport said.

“Traffic is heavy in both directions on the M7 so motorists should allow plenty of extra travel time.”

Motorists have been asked to exercise caution with emergency services and traffic crews on site.