An explosion at a Simpson Timber Co. (search) mill injured five people Wednesday morning, a police dispatcher said.

One of the injured was flown to Harborview Medical Center (search) in Seattle (search). The dispatcher said the explosion, reported shortly before 8 a.m., occurred in a compressor unit.

Simpson spokeswoman Bev Holland said she did not immediately have any details about the explosion.

"It's all smoke. The whole mill is covered in smoke," nearby resident Mike Robbins told KCPQ-TV, the local Fox affiliate.