UPDATE 4:15 p.m.
Officials confirmed the fire was also arson. Bartholomew said there were some differences in this case, and federal officials are treating it as separate incident
"Individuals who maliciously set fires threaten the safety of individuals in community," he said.
There are more than 200 employees at the site daily who are constantly coming and going, he added.
The sixth fire in less than a month sparked at the $216 million, 27-floor residence hall rising from Temple University on North Broad Street this morning, federal officials said.
Arson caused upward of $100,000 in property damages to the building in early February, officials said. No suspects are in custody at this time.
Bureau of Alcohol, Tobacco, Firearms, and Explosives Spokesman Steven Bartholomew said the sixth fire was reported around 9:45 a.m. The fire started inside a trash container on the 14th floor.
Bartholomew said the fire's cause has not been determined.
There have been no injuries or significant damages reported.
The ATF has received responses for its offer of a $15,000 reward for information that will lead to the capture of those responsible for the original five fires. Bartholomew said the ATF has learned information pertaining to the five arson fires, and investigators are following up on those leads. In the meantime, the reward is still available.
The Philadelphia Field Division of the ATF would contribute $5,000 and the L.F. Driscoll Company would contribute up to $10,000. Officials said the first five fires, which occurred on the 11th, 12th and 16th floors, were intentional.