The city's Mural Arts Program is trying to figure out who recently painted a giant black square over a tribute in North Philadelphia to a prominent African American artist.
There were initial fears that it was an act of vandalism, but program officials now suspect that it may have been the work of a firm contracted by the government to paint over graffiti.
"It's definitely possible they painted it out," said Jenn McCreary, the program's director of communication.
For now, McCreary said Wednesday, it's a mystery and a tragic loss.
A Tribute to Dox Thrash was painted in 2001 on the side of a three-story house at 2442 Cecil B. Moore Ave.
Thrash was a Georgia native who moved to Philadelphia and became a printmaker known for inventing a technique called carborundum mezzotint that he used to establish his distinctive black-and-white style.
The mural was designed by Cavin Jones and painted by Eric Okdeh in coordination with a Thrash exhibition at the Philadelphia Museum of Art.
It was part of the program's African American Iconic Images Collection and featured in an audio tour narrated by Ahmir "?uestlove" Thompson of the Grammy Award-winning band the Roots.
Over the weekend, the program was alerted via Twitter that something had happened to the mural, McCreary said.
On Monday, the program received a call from someone professing to be the property owner and saying the mural had been obliterated.
The program sent a worker to photograph the building and ask residents if they saw what happened.
There was one clue on the building: a notice that the building was not occupied and had been sealed.
Program officials learned that the property had been foreclosed on and was being managed by the U.S. Department of Housing and Urban Development.
In talks with HUD, program officials learned that a contractor might have been responsible for painting over the mural, McCreary said.
If that is the case, she said, such incidents need to be prevented.
Meanwhile, McCreary said, it is "definitely possible" that the mural can be restored.
"We would need to look at funding sources for a restoration or redo of this piece," she said.