The tip came from an unnamed woman who stopped an officer Saturday night, two days after the ambush shooting of Officer Jesse Hartnett.
"There might not be anything to it, but we're not going to take any chances with that," said Philadelphia Police Commissioner Richard Ross on Monday. "We've got to protect our police officers. That's paramount."
According to a police report written after the tip came in, the woman said the threat is not over, that the offender who shot Officer Hartnett is part of a group that consists of three others.
The woman added that Edward Archer of Yeadon is not the most radical of the four.
Archer was charged over the weekend with attempted murder for unprovoked attack on Officer Hartnett. Police say he has told them he did it in the name of Islam.
The police report goes on to say the other three males still frequent the 6100 block of Pine Street, and that the tipster warned police to be careful.
Officers are now patrolling in pairs.
"It started with the shooting," said Ross. "But as a result of the tip we are going to extend it as long as we think it's necessary.
The tipster told the officer Archer was a member of a mosque on 60th Street, but became more radical after he attended a mosque at 45th and Walnut streets in West Philadelphia.
That's where the Association of Islamic Charitable Projects (AICP) is headquartered.
"It's very easy to throw accusations around," said Walid Dimachkie, an AICP administrator.
Dimachkie told Action News he doesn't know Archer, and that Archer holds no organized role at the mosque or in the AICP.
He said the mosque has an open-door policy, so it's possible that, like many other community members, he has visited the mosque for classes or prayer.
The AICP denounces his actions.
"We have at no point taken any stance other than moderation," Dimachkie said, "preaching against extremism and, really, this extreme ideology that promotes actions like the one we witnessed."