Some 300 endangered sea turtles were found dead floating in the waters off Mexico's southern coast Tuesday after they were caught in fishing nets.
The deaths come days after more than a hundred of the same species perished due to unknown causes.
Fishers discovered the dead olive ridley sea turtles in the southern state of Oaxaca on Mexico's Pacific coast in a sector called the Barra de Colotepec, Oaxaca's civil protection coordinator Heliodoro Diaz told Reuters.
Images captured by Reuters showed dozens of dead turtles, many of them in a state of decomposition, lined up through what looked like a mesh or in groups.
The olive ridleys, chelonians in danger of extinction, measure about 75 centimeters (29 inches) and weigh around 45 kilos (99 pounds). They arrive en masse on Mexico's Pacific coast every year to spawn between June and September, with some coming as early as May.
The Latin American country, where six of the seven species of marine turtles that exist in the world nest, has a permanent protection programme for the reptiles which includes a complete ban on killing turtles, use of turtle excluder devices in trawl nets, and protection of spawning areas, among other measures including prison sentences for those who kill them.
Mexico's office of the federal attorney for environmental protection (PROFEPA) said it was investigating the case.
In another case, earlier this month, authorities said they were investigating the deaths of 113 sea turtles at risk of extinction - 102 olive ridley turtles, six hawksbills, and five belonging to the green turtle species - in a sanctuary in the southern state of Chiapas.
Experts said asphyxiation, fish hooks or harmful algae could have killed the turtles, but the cause is still being investigated, PROFEPA noted.