Fires were set in the drapery sections of both the Hecht's and Woodward & Lothrop department stores at the Columbia Mall yesterday afternoon, officials reported.
Damage is believed to total as much as $200,000, investigators said.
Employees and customers at both stores discovered the fires shortly before 4:30 p.m., said Deputy Maryland Fire Marshal Bob Thomas.
Both stores were evacuated and the fires were quickly extinguished by the stores' sprinkler systems before Howard County firefighters arrived.
The stores are at opposite ends of the mall in Howard County.
State fire investigators determined that the fires had been deliberately set and in a similar fashion. No suspects had been identified last night, Mr. Thomas said.
The fire at the Woodward & Lothrop store caused an estimated $100,000 damage.
There was no immediate estimate of the damage caused to the Hecht's store but Mr. Thomas said it was comparable to that left by the other fire.
No one was injured.
Officials of both stores said they would be open for business today.
The state fire marshal asked that any employee or customer who might have seen anyone setting a fire in either store contact investigators at (800) 492-7529