The photographer, identified only as Agnieszka, said she was aboard a train from Warsaw to Szczecin when she walked into the lavatory and saw the toilet was covered in ice and snow, The Daily Telegraph reported Wednesday.
"I took the picture this to show the conditions of toilet trains in winter," the photographer said. "Thankfully the others were in a working condition."
The photo made the rounds on the Internet and became internationally viral.
Michal Stilger, spokesman for railway company Przewozy Regionalne, blamed a faulty window for the iced-over commode.
"The condition was caused by an unsealed window," he said. "An unsealed window or door in winter conditions at high speed can suck the snow in."