Scientists believe they can now explain the mass graveyard of ancient whale fossils and other marine life discovered beside the Pan-American Highway in Chile.
The fossils - preserved more than five million years ago - are the result of four mass strandings, according to a study published in the Royal Society Journal.
Researchers uncovered strong evidence to suggest that the whales died after ingesting naturally-occurring toxic algae. The dead animals were then swept into an estuary and onto flat land where they they were eventually buried by sand.
Orange splotches in the rock near the marine skeletons - found by the team of researchers - further supported this theory. A closer look through a high-power microscope found tiny spheres similar to those found in toxins produced by certain species of plankton.
When plankton blooms in thick mats, due to rapid fertilization, toxins can accumulate and harm nearby marine life, according to Live Science. However, researchers cannot confirm that this is the case, as the spheres have become degraded over time.
"It's a good candidate, but we can't exclude the possibility that these have a geological origin," study co-author Nicholas Pyenson, a researcher at the Smithsonian, told Live Science. He said other possible causes for these mass die-offs could include tsunamis and viruses, but in this case there is no evidence of a tsunami, and viruses do not usually affect a wide range of species.
The graveyard was discovered in 2010, during an expansion project of the Pan-American Highway in northern Chile. Since the amazing discovery, the site has been nicknamed Cerro Ballena, or "whale hill."Chilean and American paleontologists were given just two weeks to conduct their research before the highway construction project resumed.