Federal investigators have found no misconduct by U.S. Forest Service personnel in the deaths of five firefighters in a massive 2006 California wildfire.

Under federal law, the inspector general for the Department of Agriculture is required to investigate the death of any U.S. Forest Service firefighter entrapped by a wildfire. Inspector General Phyllis Fong said the fatalities resulted from the rapid and unexpected behavior of the fire as well as a lack of "adequate situational awareness" among firefighters.

However, she stressed that the deaths did not occur as a result of "misconduct or unauthorized actions by (Forest Service) personnel."

The blaze known as the Esperanza fire swept through valleys and mountains about 90 miles east of Los Angeles. Ultimately, the fire destroyed 34 homes and blackened nearly 70 square miles. The five U.S. Forest Service firefighters were killed while attempting to protect an unoccupied house.

One witness told investigators that, in a brief period lasting no more than 15 seconds, the crew's situation deteriorated from one not perceived as posing imminent danger to one that was "overwhelmed by a burnover," Fong said in a letter to Agriculture Secretary Tom Vilsack.

The man who started the fire, a serial arsonist named Raymond Lee Oyler, has been sentenced to death.

The firefighting community was relieved by the findings but some said they were still anxious about possible fallout from the fire deaths.

Federal prosecutors have five years to decide if they will file criminal charges against anyone else in the case, including firefighters, said Casey Judd, business manager for the Federal Wildland Fire Service Association, an advocacy group.

"There's still two years to fret about whether anybody on that fire may be called out for whatever they did," he said. "Just because the report is out ... doesn't necessarily preclude the government from doing some nutty thing and going after somebody."

John Heil, Forest Service spokesman, did not immediately return a call seeking comment.