The head of a federal board investigating last week's deadly Bayer CropScience plant explosion says the probe will take at least six months.

U.S. Chemical Safety Board Chairman John Bresland said at a news conference Sunday the investigation will begin with a tank at the center of the blast and what the vessel contained. Bresland says the investigation could last a year.

A five-member team from the board is expected to be in Institute until Friday, then return as needed. The agency is charged with investigating industrial chemical accidents.

The explosion late last Thursday occurred in a section of the plant where waste products are treated before disposal.

One worker was killed and another suffered burns.