One teen bashed a rider in the face with a soda-pop can, pushed him down and stole his wallet. Another passenger was punched in the face during the Saturday night attacks just south of downtown Atlanta.
The riders, both of whom are Delta Air Lines employees, suffered cuts to their faces.
There were surveillance cameras at the station where the suspects boarded the train, but there is no video from inside the train car, said Lyle Harris, a spokesman for the Metropolitan Atlanta Rapid Transit Authority.
Harris said the attacks were a rare occurrence, and that MARTA is constantly reviewing how its officers are deployed.
State Rep. Mike Jacobs said Friday he wants to know more about whether MARTA is adequately protecting passengers, and he hopes to learn about that issue at a May 3 public hearing in the Coverdell Legislative Office Building near the Georgia Capitol. Jacobs is chairman of a MARTA oversight committee.
"If not properly addressed, I think this incident has the potential to shake customer confidence at some level," Jacobs said of Saturday's attacks.
Jacobs, who travels on MARTA trains, says he's noticed fewer uniformed officers on the trains.
MARTA "has not and will not compromise the safety and security of its system or its customers," the transit authority said in a statement Friday.
"The fact is that this unfortunate crime could have easily happened anywhere," MARTA's statement said.