The first incident happened at the Snyder Avenue station on Tuesday afternoon. He was seen on surveillance camera snapping photos in the area around the tracks. Police are not releasing his picture, just saying he's a white man in his 20s with a ponytail. He was also carrying a backpack.
"We would be very happy to talk to talk to this individual to we can determine there was a legitimate reason, or a non-criminal or non-threatenin reason for the pictures being taken," said Chief Insp. Joseph Sullivan of the Philadelphia Police.
Then, on Wednesday evening, a SEPTA cashier at the Broad and Lombard station noticed a man she described as "middle eastern" taking pictures. He showed her pictures of other subway locations, then started to delete the images.
Police do not believe the two incidents are related to each other, or the high-profile terrorism cases of recent days.
"We are very closely monitoring the situation in New York, ensuring there is no connection to Philadelphia. At this point, there is not," Sullivan said.
SEPTA is more than halfway through the process of installing highly sophisticated surveillance cameras in all of its 60 subway stations. In fact, the person of interest in the Snyder Avenue incident was captured on one of those cameras.
In light of the national events, SEPTA is not surprised to be getting added tip calls from an alarmed public.
"In the aftermath of something like the arrest, it's not unusual for us to receive calls, one or two calls a day from people about people doing other things like taking photographs around subways or equipment," said SEPTA Public Safety Director James Jordan.
A lot of SEPTA's riders have ongoing worries about possible terrorist attacks stemming back to 9/11.
"I don't even fly like I used to. You're afraid they're on planes or wherever," said Mary Lorenzo of South Philadelphia.
Authorities say they do appreciate those tips calls, saying if you report something suspicious, they will check it out.