Over 400 dead sea turtles have been found on India's east coast near the city of Chennai in the last two weeks.
Those numbers have not been seen in more than 20 years.
The species of turtle is known as olive ridley.
The animals travel thousands of kilometers for ideal places to lay their eggs along India's coast.
But that process, called nesting, has become more difficult because undisturbed beaches are becoming harder to find around the world.
And, mass deaths like these can be caused by fishing nets that can catch and harm the species.
Shravan Krishnan is a volunteer with Chennai-based Students Sea Turtles Conservation Network.
He told The Associated Press that in a usual year, there are between 100 to 200 adult turtle deaths on the city's coast.
"This year, we've already crossed 200 dead turtles in a little more than two weeks," he said.
Krishnan is also concerned about the low number of turtles nesting on shore.
He and other conservationists walk along the city's beaches at night to collect and move turtle nests.
They do so to prevent the eggs from being eaten by dogs or damaged by people walking along the coast.
"We have found only four nests so far, which is also really worrying," Krishnan said.
Environmentalists and forest department officials have been seeing at least ten dead turtles every day for the past few days, sometimes many more.
That is the highest number officials have seen since 2014.
Experts say the deaths are most likely caused by large fishing nets that are pulled along the ocean floor.
Manish Meena is in charge of the city's wildlife.
He said groups have been actively trying to inform people involved in fishing to release turtles that might get caught in nets.
They have also asked the coast guard to watch for illegal fishing activity.
Fishing boats using giant nets that catch everything on the ocean floor are barred by a local government order from operating within five nautical miles of the coastline during the turtle nesting season.
The law also requires the use of devices that can help turtles escape nets.
Shantanu Kalambi is an ocean animal specialist with the conservation organization ReefWatch.
He said that when the turtles get caught in nets, they are unable to come up to the surface for air.
And environmentalists say the crews of fishing boats do not always use the devices to help turtles escape, since they reduce how many fish they can catch.
Olive ridley turtles are considered an endangered species.
Just like most sea turtles, their eggs need two months to hatch.
This places them at higher risk because of coastal land activity, warmer temperatures and pollution from light.
Farther up India's east coast, over 500,000 turtles nest every year.
But only one in about 1,000 turtle babies that hatch survives to adulthood.
Experts say the turtles are important to the balance of the ocean ecosystem.
"As a species, they are millions of years old and they play an essential role in the food chain," Kalambi said.
I'm Jill Robbins.