BARTOW, Fla. (WFLA) — A medical examiner in Polk County performed autopsies Wednesday on the five victims who died in a Christmas Eve plane crash in Bartow.

The examiner ruled that 24-year-old Olivia Shannon, 26-year-old Victoria Shannon-Worthington, 27-year-old Peter Worthington and 32-year-old Krista Clayton died from blunt force trauma. The medical examiner says all four passengers’ manners of death were ruled accidental.

The cause of death for the pilot, 70-year-old John Shannon, has not been released pending a toxicology report.

Deputies say all five were killed when the small plane they were on crashed shortly after taking off from the Bartow Municipal Airport Sunday morning. The group was planning on spending Christmas Eve in Key West and was expected to return Sunday night.

Polk County Sheriff Grady Judd says he believes it was too foggy to take off. Visibility in the area was near-zero at the time.

Federal Aviation Administration records show that John Shannon was instrument rated, which means he was trained to fly without seeing the horizon, relying only on the instruments on-board if needed.

Investigators are still trying to figure out why the plane went down.