At least five years have passed since a seal broke in the third-floor window at Milton Hospital, Massachusetts, turning the glass a blotchy white. But last week the murky patches began taking a form that looks like the Madonna.
"It seems like every day it gets clearer," said Sharon McGarty, an administrator in a doctor's office across the hall. "It used to look like just a dirty window."
News of the image has spread by word-of-mouth and the media, attracting more than 25,000 people to the hospital wall containing the window and turning it into an impromptu religious shrine.
Dozens of bouquets have been placed beneath it. A large plastic container for money has also been provided.
Hospital officials have sought advice from the Archdiocese of Boston "on what appropriate steps to take" about the phenomenon.
Archdiocese spokesman, the Rev Christopher Coyne, said officials had not ruled on the image's validity but added: "If it leads to a deepening of faith ... it's a good thing."
Experts say the image is the product of a spreading chemical deposit trapped in the window pane.
"The phenomenon is basically the human ability to see pictures out of randomness. There are trillions of these and they just wait for someone to notice them," said Joe Nickell, a senior research fellow at the Committee for the Scientific Investigation of Claims of the Paranormal.
