MORGANTON, N.C. -- One man is in serious condition and another is in critical condition after an explosion at a chemical plant in Morganton Tuesday.

The plant's maintenance head, Curtis "Butch" Brackett of Morganton, was in critical condition Wednesday morning with burns at Wake Forest University Baptist Medical Center in Winston-Salem.

Plant manager Dick Edwardson of Gastonia suffered head injuries and was in serious condition at Carolinas Medical Center in Charlotte.

14 people with less serious injuries were treated Tuesday at Grace Hospital in Morganton. That group included workers and people in the vicinity of the plant, who mainly had bumps, bruises and cuts.

A voluntary evacuation is in effect for people living near the Synthron Chemical Plant in Morganton. Officials said those who stay should take shelter in their homes by shutting all windows and doors and turning off heat/air conditioning units.

An explosion was reported at the plant shortly before 11:30 a.m Tuesday.

That's near the intersection of Amherst and Kirksey roads. Officials said the area around Vine Arden Road and Highway 70 was shut down and people are asked to avoid the area.

Synthron employees 18 people in the Morganton facility. It is a subsidiary of Paris-based Protex International, a company that manufactures specialty chemicals in the United States, Europe, Asia and North Africa. Company officials in Paris declined to comment on the explosion Wednesday.