Ever since a highway construction crew in Chile uncovered a fossil graveyard of some 40 prehistoric whales in 2010, with skeletons dating back more than five million years, scientists have wondered why so many giant animals died in one place.

This week, a team of them proposed an answer: The huge baleen whales were felled by microscopic algae.

Toxins produced by prehistoric algal blooms could have been potent enough to kill off massive numbers of marine animals, according to a study published Thursday in the journal Proceedings of the Royal Society B.

The fossil site, uncovered by a road crew working on a stretch of Pan-American highway in the Atacama Desert, has yielded complete and nearly complete fossil baleen whale