(CNN) -- The youngest survivor of a plane crash that killed former Sen. Ted Stevens last week has been released from a hospital in Alaska, according to his family.
Willy Phillips Jr., 13, was released from Children's Hospital at Providence Alaska Medical Center and is traveling back to his home state of Maryland, his mother said in a statement Saturday.
Willy's father, former Stevens staffer Bill Phillips, was among the five people killed in the crash Monday night near Dillingham, Alaska.
In the statement, Janet Phillips thanked first-responders and other medical personnel "for their heroic efforts the night they spent on the mountain with Willy. Thank you for bringing Willy back."
Phillips also extended her condolences to the other families who lost loved ones in the wreck.
"Bill and our boys shared many Alaska memories," Phillips said in the statement. "They loved Alaska, and as we leave we know Alaska will remain imprinted on our hearts."
In addition to Willy, the survivors of the crash are former NASA administrator Sean O'Keefe and his 19-year-old son, Kevin, and Jim Moorhard of Alexandria, Virginia.
Killed in the crash were Bill Phillips Sr., Stevens, 86; pilot Terry Smith, 62, of Eagle River, Alaska; Dana Tindall, 48, of Anchorage, Alaska; and Corey Tindall, 16, of Anchorage, Alaska.
A memorial service for the elder Phillips will be held Friday in Potomac, Maryland, according to the statement.
Meanwhile, federal investigators continue to probe what caused the plane to crash into a rugged mountainside in southwestern Alaska, according to the National Transportation Safety Board.
Alaska Air National Guard rescuers were hampered by poor weather and terrain -- slogging for hours through rain, fog and wind to reach the site of the plane crash.
Autopsies on the five victims found the deaths were the result of blunt force trauma, Greg Wilkinson, an official at the medical examiner's office, said Friday. He said the state medical examiner, Dr. Katherine Raven, found the injuries to be consistent with this type of crash.
Raven also found that the injuries were not survivable, he said.
A funeral for Stevens, who served in the U.S. Senate for 40 years, will be held Wednesday at the Anchorage Baptist Temple in Anchorage.