Archaeologists in hard hats and face masks carefully remove earth from around enormous bones at the site of Mexico City's new airport, where construction work has uncovered a huge trove of mammoth skeletons.

Paleontologists work on the skeletons of mammoths in Zumpango on Tuesday. Photo: AFP

The remains of dozens of the extinct giants and other prehistoric creatures have been found in Zumpango on the northern edge of the capital, which sits on an ancient lake bed.

"More than 100 individual mammoths, individual camels, horses, bison, fish, birds, antelopes and rodents have already been recovered," said army captain Jesus Cantoral, who heads the excavation team. In total remains have been found at 194 spots across the site since the first discoveries were made in October 2019 during work on a fuel terminal, he told AFP.

Most of the animals are believed to have roamed the Earth between 10,000 and 25,000 years ago. Experts worked painstakingly to extract the bones of one of the mammoth skeletons, taking care not to disturb a mound of earth supporting another specimen. 

At the same time thousands of construction workers continued to labor away across the site as dozens of excavators and trucks shifted earth and transported building materials.

The authorities say they have kept a careful watch to ensure the precious remains are preserved during work on the airport, which President Andres Manuel Lopez Obrador has promised will be inaugurated in March 2022.

Experts believe the mammoths were drawn to the area by food and water provided by a lake that existed in prehistoric times.    

"The place had a lot of natural resources, enough for these individuals to survive for a long time and for many generations," said archaeologist Araceli Yanez.