UPDATED: 4:28 p.m.
Officials believe it's a 2-year-old black bear, and they think it's the same bear that was spotted up in in Bucks and Montgomery counties in recent days.
The believe the bear entered the city through a series of trails along the Wissahickon Park into the Fairmount Park area, and they say the bear has been moving unusually fast.
Authorities left after about two hours of searching, and advised neighborhood residents to be vigilant and call 911 if they spot the bear. They hope to find the bear soon, tranquilize it and get it moved to a more appropriate habitat.
SEPTA said its Manayunk-Norristown Regional Rail trains were moving slowly near the East Falls Station, the last place news helicopters spotted the bear.
Police were at the station, warning people of the sighting along the tracks along Cresson Street between Midvale Avenue and School House Lane.
Besides the slowdown, the transit agency said there was no impact to service on the Manayunk-Norristown Line.
What to do if you encounter a bear
With several bear sightings in the area, it's a good idea to know what to do if you happen to encounter one.
Duane Diefenbach, adjunct professor of wildlife ecology at Pennsylvania State University, says the black bears exploring the Delaware Valley are likely yearling males who've been run off by their mothers.
"They're trying to find a new territory that they can set up where there aren't older male bears around, so they usually end up in places where they run into problems," Diefenbach said.
And those are human made.
"The bear's in greater danger than people, because it's likely to get hit by a car or just get into a situation that's too dangerous," he said.
Bears will eat whatever is around, so Diefenbach says to make sure to remove temptations like pet food, bird feeders and garbage. In the unlikely event that you find yourself face-to-face with a bear, "my guess is that the bear's gonna run away faster than you can," he said.
But if it doesn't, Diefenbach said to "just back up, and slowly move backwards and in a direction that you're not cornering or threatening the animal."
And, he says, make sure you report the sighting to authorities so they can track down the bear and relocate it to a more appropriate habitat.
The Pennsylvania Game Commission has more information on black bears and bear encounters here.