Video by Gretchen Mollenhour

Vehicles flooded into Downtown Friday when Interstate 229 was closed because of smoke from a chemical fire on South Fourth Street.

Dispatchers scrambled four St. Joseph Fire Department companies after a 6:10 a.m. emergency call.

The fire was in a warehouse at 1302 S. Fourth St., said John Nelson, one of three Fire Department battalion commanders on the scene. Tons of herbicide chemicals called atrazine are stored in the structure, Mr. Nelson said.

At 6:20 a.m., Russell Moore, the incident commander, requested the interstate closure. Southbound vehicles were diverted into the Downtown area until about 8 a.m., when I-229 reopened.

The herbicides delayed and complicated firefighter efforts. Crews were using as little water as possible to fight the blaze.

This was an effort to avoid dangerous chemical reactions and minimize water runoff, Mr. Nelson said.

The building is owned by local businessman Steve Crawford. Mr. Crawford said the building has no electrical power and that the chemicals stored there are not explosive.

The department used vans to ferry fresh crews of firefighters to the scene. Firefighters brought the blaze under control at about 8:25 a.m.

Firefighters from Engine 1 and 11 sustained significant exposure to the herbicide, Mr. Nelson said. The smoke is much worse than the product itself, he said.

As a safety precaution, the department followed decontamination procedures. Shortly after 9 a.m., the Northwest Missouri Region H Hazardous Materials response team started cleanup work, and city crews joined the effort, hauling concrete blocks and earth to the site. At 9:45 a.m., Mr. Moore said the fire was out.

The Environmental Protection Agency was notified of the incident. Missouri’s Department of Natural Resources hazardous materials personnel were on the scene.

Friday afternoon, Jason Ziph, a fire inspector, ruled that the blaze had an undetermined origin. The building hadn’t been properly secured, Mr. Ziph said. Damage to the building was estimated at $5,000.

Mr. Crawford will be responsible for the cleanup and must meet all DNR and EPA standards, said Bill Brinton, Buchanan County’s emergency management coordinator.

Marshall White can be reached

at marshallnpgco.com.