Health officials are hoping to learn more about the possible toxic effects from clouds of smoke that continued to hover over the city Tuesday following an explosion and fire at a pharmaceutical lab.

Residents near the Ferguson Pharmaceutical laboratories were evacuated Monday after an explosion in the building.During the evening, as the smoke lowered over Rexburg and nearby Sugar City, many residents began complaining of headaches, sore throats and breathing problems, a Madison County sheriff's dispatcher said.

Because of possible toxic effects, Madison County officials continued to recommend that evacuated residents stay away from their homes and to try to reach fresh air.