Police say residents of a west-side neighborhood called to report buffalo standing in the street, saying they didn't know what to do.
Two officers were dispatched to the scene Monday, and used a flashlight to herd the animals back to a pen from which they appeared to have escaped.
A man showed up at the pen saying he was in charge of the buffalo and thanked the policemen for returning them, but police say they will investigate whether the animals are being properly held there.
More than 20 million people live in the megalopolis that is Mexico City and its surrounding suburbs -- an urban home where buffalo aren't known to usually roam.
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