The Putin government’s expanding crackdown on political dissent has entangled one of Russia’s most iconic and respected institutions: Moscow’s famously ornate Metro system.

Over the last week, dozens — perhaps even hundreds — of train drivers, mechanics, ticket agents and other public transit workers have been hauled before management and told to either resign or be fired.

The reason appears to be that either they or a family member signed onto a website calling for President Vladimir Putin’s arch-foe, Alexei Navalny, to be freed