Law enforcement agents say anti-terrorism raids conducted in New York City, Monday, were part of an ongoing investigation centering around a man allegedly linked to al Qaeda.
The man's visit to the borough of Queens over the weekend set the raids into motion.
Just days after the anniversary of 9/11, authorities believe they may have broken up another major terrorist plot.
Click play for more of Erick Stakelbeck's comments, including analysis on warnings from FBI and Homeland Security officials to be on the lookout for materials that could be used to make explosives.
Members of a joint terrorism task force raided several apartments in a heavily Muslim Queens neighborhood early Monday morning.
They were searching for bomb-making materials, which they did not find, but 26-year-old Afghan native Niav Khan was questioned by investigators.
He told reporters he was not plotting to build a bomb.
"We don't have anything like that," Khan said.
Authorities did seize several documents, computers and cell phones.
They described the potential threat as real and urgent. Members of Congress were briefed following the raids.
"They would not have moved as quickly as they did if they did not believe there was real potential perhaps more than that," said Rep. Peter King, R-N.Y.
Several Afghan men were taken into custody in connection with the investigation, but have since been released.
It was their meetings in Queens this weekend with a suspected al Qaeda associate that sparked the raids.
The man-- an Afghan national living in Denver, Colo.--has been under federal surveillance. Police said he had recently visited Pakistan and brought bomb-making documents with him on his trip to New York City.
"There was very good reason to believe that there is a connection to al Qaeda or to al Qaeda supporters," Rep. King added. "This does not appear to be self starters."