ALBUQUERQUE, N.M. (AP) — Evidence indicates that a helicopter that crashed in northern New Mexico after helping fight a wildfire over the weekend descended at a fast rate, with the craft ending up mangled and in pieces after first hitting the ground upright, the National Transportation Safety Board said Monday.

The agency has completed its initial documentation of the deadly crash, but it will likely take weeks for investigators to determine the cause. Authorities were in the process of removing the wreckage from a remote area south of the community of Las Vegas to a secure location where it could be examined further.

The helicopter was carrying three people with the Bernalillo County Sheriff’s Office and a county firefighter when it went down Saturday evening while returning from its firefighting mission. County officials on Monday called the four men heroes.

“It is with a sad and broken heart that we think of the heroes we lost this weekend," Sheriff Manuel Gonzales and Fire Chief Greg Perez said in a joint statement. “The reality is that we will likely grieve this loss forever. Each of these heroes died doing what they loved, serving others. They paid the ultimate price, and we are forever grateful to these men for the love and passion they had as first responders.”

Authorities had scheduled a news conference for Monday afternoon in Albuquerque.