Long ago, there was a vast network of lakes and canals that was a key part of Aztec civilization in what's now Mexico City. A very strange creature took up residence there.

It was called the axolotl, and it was a foot-long salamander that looked like a fish with legs. The locals came to call it the "water monster" and the "walking fish."

Well, those lakes and canals in Mexico City's Xochimilco borough are mostly gone now — or badly polluted. It seems the axolotl may be just about gone too.

Biologist Armando Tovar Garza of Mexico's National Autonomous University says researchers spent four months last year skimming the muddy waters of Xochimilco and found "zero" axolotls.

There are still some of the creatures in captivity, but Tovar Garza says the axolotl "is in serious risk of disappearing" from the wild — if it hasn't already.

Garza's not ready to close the book on the monster though.

He says researchers will start another search in early February, the beginning of the axolotl's breeding season.