Emergency personnel Tuesday dealt with a mock disaster drill — then got a call about a real potential disaster.

At 10 a.m., emergency personnel from Southwest Mississippi Regional Medical Center, McComb police and fire departments and Pike County civil defense and sheriff’s departments held an hour-long drill involving a fictitious anhydrous ammonia spill.

Around 5 p.m., McComb firemen got a call about mysterious chemical barrels that had been placed in the back of a customer’s pickup truck at McDonald’s Restaurant on Delaware Avenue.

Once again firemen donned their hazardous materials suits, but some investigation determined that situation was not a disaster.

McComb Fire Chief Vernell Felder said this morning that a Sanderson Farms employee was supposed to drop off the barrels — which contained a chemical used at the poultry processing plant — in an awaiting truck at the fast-food restaurant.

However, the employee’s son put the barrels in the wrong vehicle. When the truck’s owner left the restaurant and found the barrels, he called officials.

“He did the right thing,” Felder said, noting that firefighters treated the barrels as if they contained hazardous materials until they were sure of their contents.

In the mock drill scenario, an 18-wheeler filled with ammonia blew a tire on the frontage road by Edgewood Mall. Leaking ammonia left the driver unconscious, and a staged wreck occurred as passers-by slowed to look.

In all there were 13 fictitious patients. Emergency personnel had to respond as though the situation were real.

“There are a few areas that need tweaking, but for our first time it went over well,” said civil defense director Richard Coghlan.

Hospital spokesman Gary Heim said the glitches mainly involved communication.

“There were too many lines of communication, and that’s normal,” he said. Otherwise, “We worked together well as a team.”