Sgt. Pete Van Arnum recalled hearing tales of Mafia members dumping bodies in Lake Tahoe back in the 1950s.

“That may or may not be true, but we can’t be sure because we can’t go down that far,” said Van Arnum, a member of the El Dorado County Sheriff’s Department and former coroner.

What, or whom, Lake Tahoe holds in its average depth of 1,000 feet is a mystery, except for those who have lost family or friends in drownings, boating accidents or other fatal mishaps. But the conditions within the second-deepest lake in the United States keeps the mystery unanswerable.

An autopsy on an unidentified woman’s body found Friday in the lake indicated no immediate cause of death, said Lt. Mike Biaggini of the Douglas County Sheriff’s Department.

The cause of death will have to be determined by microscopic and toxicology tests, Biaggini said. DNA tests and dental records could be used to identify the woman.

The discovery of the body in shallow waters near Glenbrook perplexed some officials with knowledge on how the lake keeps its victims.

“Usually a person who goes into the lake, they don’t come back up,” said Mike McFarlane of McFarlane Mortuary.

“I just never, never have seen anyone floating,” he added. “They usually go down and that’s it.”

“We’ve had a number of cases over the years where drowning victims, or apparent drowning victims, never surfaced again,” said El Dorado county sheriff’s Lt. Les Lovell. “They’re just gone.”

An incident last summer involved a man from India, whose friends reported seeing him drown in water 700 feet deep after he fell into the water off a flotation device. He was wearing a life vest, which was later found floating by itself. The case was filed as a missing person in the event his body ever surfaces.

A number of factors contribute to the phenomenon, according to Dr. Anton Sohn, chairman of the pathology department at the University of Nevada in Reno.

When people drown, for instance, their lungs fill with water, dropping them into the depths of the lake.

Death brings decomposition where bacteria consumes bodily flesh at some pace. During that process gases such as methane, nitrogen and oxygen are produced but the type of gases formed depend on the type of bacteria in the gastrointestinal tract, Sohn said.

The gases would allow a body to rise “like a balloon. The body buoys up to the top,” Sohn said.

Since the lake has frigid temperatures bodies don’t decompose, thus gases don’t form, prompting them to stay submerged.

Lake Tahoe has a constant temperature of 39 degrees between the depths of 600 to 700 feet, according to the U.S. Geological Survey. It’s surface temperature varies with the type of season. In months such as August and September the surface temperature runs between 65 to 70 degrees. During this time of year the surface temperature as cold as 40 degrees and as warm as 50 degrees.

On Friday the temperature in Lake Tahoe was 39 degrees while the surface temperature was 44 degrees, according to the U.S. Coast Guard.

The refrigerator at McFarlane Mortuary where bodies are kept to fight off decomposition is 34 degrees, McFarlane said.

Sohn added optimal temperatures for bacteria growth in laboratories is about 100 degrees. Cut that temperature in half and bacteria doesn’t thrive, he said.

Van Arnum, the former coroner, remembers the body of Lee Taylor who died trying to break the water speed record on Lake Tahoe in November 1980. While taking a test run on the lake, Taylor’s boat hit a wake and crashed. Using a camera to spot the cockpit, Taylor’s body, still strapped in, was pulled from the lake a few weeks after the accident, Van Arnum recalled.

Taylor’s body was “perfectly preserved,” Van Arnum said.

Adding to the trouble to fetching bodies from the depths of the lake is the limited depth divers can reach because of the lake’s altitude. At sea level, divers can reach depths of 130 feet but at Lake Tahoe the maximum depth is 90 feet before a diver hits a dangerous, bends-inducing level.

Add currents, how the water “turns over” often and the various density of people and bodies can drop farther in the water.

Sohn remarked when fish and other lake carnivores nibble on bodies how gases from within the human tissue will be released, making the bodies denser.

– Tribune staff writer Amanda Fehd contributed to this report.