WHITESIDE (AP) — Two Tennessee law enforcement officers died when their helicopter hit power lines and crashed in a wooded area. The lines fell across I-24, and lanes of the highway were shut down as first responders looked for the crash site, officials said.

A Tennessee Highway Patrol officer and a Marion County deputy sheriff were killed in the crash Tuesday afternoon in Marion County, Highway Patrol Capt. Travis Plotzer said. Their names were not immediately released and he didn't take questions at a news conference.

He said the National Transportation Safety Board was leading an investigation.

The helicopter hit power lines on Aetna Mountain near Whiteside, about 15 miles west of Chattanooga, causing the lines to fall across Interstate 24, officials said.

Motorist Dan Hostetler told WVLT-TV that he saw a black helicopter flying in circles before he narrowly missed getting hit by the electrical cables.

"It kind of dipped a little bit and waggled a little bit then there was a bright flash of light and puff of smoke and it hit one of the power lines that went across the highway, and sure enough the power lines started gliding down toward me and all I could think was it's going to land on top of me," Hostetler said. "I slammed on the brakes and stopped about 2 car lengths from the line."