One of the cars' owners reported the crime, in the 5700 block of Southwestern Ave., to police around 5:10 p.m.
The vehicles were parked on the street, near but not on the lot of the Halethorpe MARC Station, said Paulette Austrich, a Maryland Transit Administration spokeswoman.
Both county and MTA police are "increasing patrols" in the area, Austrich said.
Authorities are asking anyone who has information in the case to call 410-887-0872.
Sun reporter Kevin Rector contributed to this report.