Everyone is pissed.

In Mexico City, many people who travel on the subway system blame authorities for the many broken escalators at train stops. Metro officials blame something else: “vast amounts of pee,” reports A-Pee.

Nobody's clear exactly how it happens, but human urine, in really large amounts, is “penetrating and corroding the drive wheels and mechanisms of the escalators that carry riders up from underground stations,” AP reports:

In a list published Tuesday, the Metro system listed “corrosion due to urine” as one of the top five causes of escalator breakdowns. Fermin Ramirez, the system’s assistant manager for rails and facilities, said riders appear to be urinating on escalators at off-peak hours and lightly used stations, “even though it seems hard to believe.”

“When we open up escalators for maintenance, there is always urine,” Ramirez said. Most stations have no public bathroom facilities, a fact Twitter users were quick to point out, noting there are not even any pay toilets.

Of the system’s 467 escalators, 22 are out of service on any given day.

The biggest problem, subway authorities admit, is that the many escalators are old, or have been damaged by rough use.

Mexico city plans to replace about 55 escalators over the next two years.

Read more: Mexico City subway says pee causes escalator breakdowns Read the rest

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