A sixth, aged 11, and the oldest, is being treated for burns after being airlifted to hospital in Indianapolis.

The youngest was just 17 months old, fire chief Carl Buchanon told reporters.

An adult who escaped with minor injuries tried to rescue some of the children but was forced back by heavy smoke and flames, Mr Buchanon added.

Fire crews in South Bend, a city of more than 100,000 people, fought the fire for about three hours.

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The flames spread quickly, partly because of wind, Mr Buchanon said.

One of the firefighters was treated in hospital after falling through a floor.

The cause of the fire is being investigated.