BLAINE COUNTY -- The Blaine County Sheriff's Office says the sound of explosions have caused some consternation across the county lately.

But officials are reassuring residents they are not under siege.

Blame the loud booms on Idaho Power, which has been working to replace transmission lines between Hagerman and the Wood River Valley. Crews use explosives to splice the power lines together.

Jeff Lincoln, the principal engineer in Idaho Power's transmision department, said the explosive devices are essentially a metal sleeve surrounded by detonation cord.

"The force of that explosion basically crimps that tube on the wire," fusing it into one piece, Lincoln said.

In addition to the loud sound, the explosion also creates a fireball five or six feet in diameter, Lincoln said, although it happens so quickly, it appears more like a flash to the naked eye.

The transmission crews go through extensive training to be able to use the explosives.

Idaho Power is currently working in the Deer Creek area, and will move on to Croy Creek and Rock Creek as the project continues. The sheriff's office says area residents may hear between four and ten loud explosions per day until the project is completed in about two weeks.