It was 2:30 p.m. Tuesday when a probation officer was checking a residence in the 700 hundred block of Ellen Drive in Bear.
That's where county police discovered hazardous materials in the residence, part of a suspected meth lab.
Four county police officers were treated and released from Christiana Hospital after inhaling some of the chemicals.
Police and crews from the Delaware Department of Natural Resources and Environmental Control spent most of the evening removing the hazardous materials.
One suspect was arrested. That person's name has not been released.