A natural gas leak forced evacuations in the eastern Iowa town of Monticello overnight. Authorities say a 60-thousand gallon tank was the source of the problem in the Jones County town. About ten families and a number of workers from nearby businesses had to be rushed to safety.Monticello fire chief Gaylen Kray says when fire crews arrived, they immediately took the appropriate precautions and called for backup.Columbia Propane owns the tank. The cause of the leak is under investigation. All families were allowed back in their homes early this morning.