Why did 10,000 endangered frogs die in Lake Titicaca in Peru?

Peru is investigating the mysterious deaths of 10,000 endangered frogs that washed up along the shores of Lake Titicaca and one of its main streams over the weekend.

Lake Titicaca, one of South America's largest lakes and the world’s highest navigable body of water, is believed to be the birthplace of the Incas.

Authorities went into action this week, when activists brought 100 frog carcasses into the main square of Puno, the largest town on Lake Titicaca. The cause of their deaths is unknown, but previous studies have warned that water quality worsening, due to pollution from illegal mining and sewage runoffs.

This story was originally published October 20, 2016 at 8:40 AM with the headline "Why did 10,000 endangered frogs die in Lake Titicaca in Peru?."