A fifth set of human remains has been found in Lake Mead in the south-west US, exposed as water levels have fallen due to drought.
Several sets of human bones have been discovered in the lake in the past couple of months, as levels have declined.
The most recent set of remains at Lake Mead, which is off the Colorado River in the states of Arizona and Nevada, were found on Monday, the National Park Service said.
"The investigation is ongoing," the service said.
The first remains were discovered in May inside a barrel. Investigators said the remains were most probably of a man who was killed by a gunshot and dumped into Lake Mead four to five decades ago.
"It's likely that we will find additional bodies that have been dumped in Lake Mead," Las Vegas homicide detective Lt Ray Spencer said at the time.
A second and third set of remains were found over summer. Another set of bones were found last week.
None of the remains have been identified or linked to any individuals in the ongoing investigations.
The discoveries have prompted speculation about long-unsolved missing people and murder cases from decades ago — to organised crime and the early days of Las Vegas, which is only a 30-minute drive from the lake.
The lake surface has dropped more than 50 metres since the reservoir was full in 1983.
The drop in the lake level comes as most scientists say the world is warming mainly because of rising levels of carbon dioxide and other greenhouse gases in the atmosphere.
Scientists say the US west, including the Colorado River basin, has become warmer and drier in the past 30 years, and led to drastic water cuts.
Sunken Second World War landing craft revealed as Lake Mead dries up - in pictures
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A sunken Second World War-era Higgins landing craft that used to be nearly 61 metres underwater is revealed near the Lake Mead Marina in the US state of Nevada as the waterline continues to fall. AFP -
The water level at Lake Mead is at its lowest since being filled in 1937. Getty -
A climate change-fueled megadrought coupled with increased water demand in the south-western US have dried up portions of the lake. Getty -
A vehicle towing a boat drives past a sign welcoming visitors to Lake Mead. The water level is at its lowest since 1937. Getty -
People paddleboard at Willow Beach in the Lake Mead National Recreation Area. Lake Mead is the largest reservoir in the US but is shrinking at a terrifying rate and now stands just one quarter full. AFP -
A 'bathtub ring', a white band of mineral deposits showing previous water levels, is illuminated at sunset at Lake Mead. AFP -
People fish and play in the water on Lake Mead. It is the largest reservoir in the US, a huge man-made body of water formed by the construction of the Hoover Dam in the early 1930s. AFP -
A sign indicates the Lake Mead waterline in 2000 in contrast to current low water levels. AFP -
The Lake Mead Marina in Nevada. Lake Mead is the largest reservoir in the US but now stands just one quarter full. AFP -
A white band of mineral deposits shows Lake Mead's previous water levels. AFP -
A formerly sunken boat is stuck nearly upright in a now-dry section of lakebed at drought-stricken Lake Mead. Getty -
Boats are docked on a drought-stricken Lake Mead. Fears are increasing that Lake Mead could become a ‘dead pool’, when the water levels become too low to flow downstream from the nearby Hoover Dam. Getty -
A mud-encrusted teddy bear sits in a formerly sunken boat. AP -
Dead and desiccated fish arranged by a visitor to the Lake Mead National Recreation Area stick out of cracked mud. AP -
Craig Miller smokes a cigarette beside his stranded houseboat. He had been living on the boat for more than two weeks after engine trouble and falling lake levels left it above the water level. AP -
A coyote walks across dry land that was once under the waters of Lake Mead. AP -
Bobby Rhinebolt, right, smokes a cigarette while sitting beside Victor Perez near a formerly sunken boat implanted upright in mud and now above the water line at Lake Mead. AP
News agencies contributed to this report
