Authorities are investigating what may have caused the roof on a Charles City, Iowa nursery to collapse.
On March 11, the roof collapsed at Sherman Nursery, causing $4 million in damages. One man said the collapse sounded like thunder, except there were no storms in the area. The 270 foot long concrete-sided building, which had a corrugated metal roof, contains about a third of the nursery's stock, which includes trees, shrubs and perennials.