A hazardous materials incident at the Burlington Northern-Santa Fe Railroad crossing at Maple Avenue in Brookfield snarled train and vehicle traffic for more than five hours on Monday.

The culprit? As of about 5 p.m. on Monday, officials say they aren't sure. All they know is that about 10 to 15 clear plastic bags containing an unknown substance apparently fell off a vehicle that was driving from north to south through the grade crossing sometime Monday morning.

The substance initially was described as a liquid, though Brookfield Fire Capt. Edward Bermann would not confirm that description at about 1:30 p.m. Two firefighters wearing orange HAZMAT suits collected samples of the substance on both ends of the crossing before entering a special mobile decontamination unit — a semi-tractor trailer belonging to MABAS Division 10 — parked on Maple Avenue south of tracks.

Because there was no identifying labels on the plastic bags and because at least a couple of the bags had been broken by cars running over them, fire officials sounded a HAZMAT spill box alarm, which triggered a huge response to the area. The bags were described as being able to hold about 16 ounces of a substance.

Vehicles from fire departments belonging to MABAS Division 10, including LaGrange, LaGrange Park, Riverside, McCook and Lyons responded to the scene. In addition, MASAS Division 10 sent their mobile decontamination unit.

Meanwhile, technicians and EMS units responded from Argonne National Laboratory, Bedford Park, Clarendon Hills, Darien-Woodridge, Downers Grove, Forest View, Pleasantview, Hinsdale, Lemont, Westmont, Western Springs, Romeoville and the Tri-State Fire Protection District.

The initial call came in just after 9 a.m., said Bermann. The box alarm was sounded at about 10:35 a.m.

"At no time was there a hazard to the public," said Bermann, who called the large response "a precaution."

The area around the grade crossing was closed to vehicle traffic for about a block in all directions. At no time, however, were residents asked to evacuate. A preschool run by the Brookfield Recreation Department on Maple Avenue just north of the grade crossing was not in session because of the Columbus Day holiday.

According to Brookfield Village Manager Keith Sbiral, initial tests indicated that the substance was some sort of harmful chemical, perhaps a nerve agent. However, after multiple tests, the substance was determined to be inert, and disposal crews were given permission to clean the site.

A Metra spokesman said train traffic was halted about noon, but no trains were running through the area prior to that time. Service was restored as of about 4:45 p.m. on Monday, although cleanup efforts were still taking place in the area after that time and vehicular traffic was still blocked.

"The issue is you can't roll the dice with something like this," Sbiral said. "You want to make sure when people see something they say something, especially when you're dealing with one of the busiest railroad tracks in the country."

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