Officials With Eastman Chemical Company, Based In Kingsport, Are Continuing To Investigate What Caused An Explosion In A Research Facility. Three People Were Injured When The Blast Blew Out Windows And Doors, But They Were Later Allowed To Return To Work. Officials Said The Damage Was Limited To That Building. Eastman Believes There Will Be No Adverse Impact To Human Health Or The Environment. Regulatory Authorities Have Been Called As Part Of Proper Procedure. The Probe Is Continuing.