MARTA is working to repair more than 100 bus shelters that were vandalized in a one-week period this month, causing at least $20,000 in damage, officials said.

The bus shelters, many of them new and clustered around Memorial Drive, were graffitied with a liquid substance that etches glass, a MARTA spokeswoman said. The etching makes the graffiti impossible to remove without replacing an entire glass panel, each of which costs about $200. In some cases, the glass was completely shattered, leaving the shelters open to the elements. The spokeswoman said most of the vandalism took place between Dec. 3 and Dec. 10.

MARTA is working to replace the panels now, but the project is taking longer than anticipated because of the number of bus shelters affected, the spokeswoman said.

MARTA police did not say if any suspects had been identified or if any of the acts of vandalism were captured on surveillance cameras.