Mexican anthropologists say they have found two human-built pits dug 15,000 years ago to trap mammoths.

Researchers from Mexico's National Institute of Anthropology and History said this week the pits were found during excavations on land that was to be used as a garbage dump.

The pits were filled with bones from at least 14 mammoths and were found in Tultepec, just north of Mexico City.

The pits were about six feet deep and 75 feet in diameter.

The institute said hunters may have chased mammoths into the traps, and remains of two other species that disappeared in the Americas, a horse and a camel, were also found.

It's unclear if plans for the dump will proceed.