Police have no suspects and don't know if the damage was the work of adults or juveniles. Knight said it is easy to get onto the former military base.
Knight said several people probably are responsible for the vandalism. The vacant buildings are easy targets, he said.
He theorized that the vandals strike in the evening and use rocks they find nearby to smash the windows to get inside the buildings.
Once inside, they've kicked walls and damaged drywall, he said.
"A lot of it has been malicious. It's just mischief but the price tag is going up," Knight said.
Some buildings at Fort Ritchie are occupied by a military transition team, by Role Models Academy for high school dropouts, and by the International Masonry Institute. PenMar, created by the Maryland General Assembly to redevelop the land for business use to replace the 2,000 jobs lost when Fort Ritchie closed in September 1998, also leases property on the base.
Knight said the damage for the most part has been limited to unoccupied military housing units.
In his search for suspects Knight said he ruled out the Role Models Academy students who board there because of their regimented schedules.
"I don't think they have the opportunity to run around. They're kept too busy," he said.
Knight said he was unsure what type of security the businesses at the base maintain.
For a few months after the base closed in 1998, sheriff's deputies were contracted to patrol the base.
"It was good deterrent," said Knight.
PenMar Board President Brett Wilson said there have been past incidents of vandalism at the base that warranted police patrols, but the recent incidents haven't thus far.
PenMar has rented out more than 100 residential units on the property, he said.
Steve Stouffer, senior site coordinator for the U.S. Army, said he does not think additional security is needed at the base.
Representatives of Role Models and International Masonry Institute did not return phone calls.