A preliminary autopsy on the body of a hiker found on a ledge 150 feet below the summit of a massive rock pillar in Utah's Zion National Park indicated no signs of foul play, officials said Tuesday.

The initial autopsy results determined Jeffery Robert Dwyer, 28, Sandpoint, Idaho, died from "massive head injuries," said Washington County Sheriff Glenwood Humphries.But Humphries said investigators still were awaiting the results of additional medical tests before ruling whether Dwyer's death was accidental, a homicide or a suicide. Until then, the cause of the death late Saturday or early Sunday remains under investigation, said park spokesman Bob Andrew.

"There's enough suspicion because of the amount of blood we found that we've ruled it a suspicious death," said Andrew.

Dwyer was traveling with two other people on a seven-week trip through the Western United States and Mexico, Andrew said. He was last seen alive on Saturday.

Tourists found a blood-stained backpack and a pool of blood Sunday on the top of Angel's Landing, a 1,500-foot-high sandstone column. A helicopter pilot spotted the body about 4:15 p.m. Sunday on the ledge, but climbers were unable to recover the victim until 11 a.m. Monday.

Andrew said Park Service officials "were concerned about all the blood on the top of Angel's Landing." And sheriff's deputies said they found a half ounce of marijuana in the victim's pocket.

The incident also was being investigated by the FBI, which has jurisdiction in deaths in national parks.