Windsor fire crews were called out to a report of fire in the duct work at the Windsor Assembly Plant around 1:30a.m. Friday morning.

Firefighters say they’re unsure what started the flames.

There were no injuries and investigators say the duct was to be discarded, so there was no estimate of damage.

Firefighters were called out to the plant earlier this week when an unrelated fire started in the ceiling.

Workers were making repairs.

In that instance, the fire was contained and again there were no injuries.

The plant is currently being upgraded for production of the next generation minivan.