At around 8 a.m. on Saturday, units assigned to the airport pulled over a speeding car that was leaving the area, according to a statement released by the Chicago Police Department.
After the 32-year-old driver was questioned, a search was performed by officers who “found an AR-15 assault rifle and a pressure cooker in the trunk of the car,” the statement noted.
Three unidentified individuals were arrested and interrogated by investigators from the city’s organized crime bureau and joint terrorism task force, according to the statement.
The pressure cooker, the statement added, “was not intended to be weaponized.” The investigators made this determination after detecting “food and grease” inside the device.
The accused driver told police he made the trip to the airport to “drop a friend off at the airport” and after “lengthy questioning” it was concluded that the driver “posed no threat to the upcoming Chicago Marathon or events in the city.”
The man’s name has not been announced, as prosecutors are still drawing up aggravated weapons charges against him, according to the statement.
The arrest comes days after the Las Vegas massacre where 58 people were killed and hundreds were injured by a lone gunman, and after three men were formally charged for attempting to "create the next 9/11" in New York in the summer of 2016.
That foiled attack in New York, according to a federal complaint, named a Canadian man hiding out in a New Jersey cabin who allegedly shipped 40 pounds of hydrogen peroxide to an undercover FBI agent.
“We really need a strong bomb,” El Bahnasawy was quoted as saying, according to the court documents.
Bahnasawy, along with two alleged accomplices -- 19-year-old Tahla Haroon, a U.S. citizen living in Pakistan and 37-year-old Filipino citizen Russell Salic -- were all named and charged, but neither Haroon or Salic has been extradited to the U.S. yet, according to the court documents.
Bahnasawy is awaiting sentencing in December.
Last Sunday, 64-year-old retiree Stephen Paddock launched a massive sniper attack when he unloaded over 20,000 bullets on country music concert goers from hundreds of yards away and 32 floors up inside the Mandalay Bay Resort & Casino in Las Vegas.
The report touted signature tactics like “vehicle ramming” and also attacking mass transit, because they remain “vulnerable targets.”
To offset any potential “threats to mass transit in Chicago” the report stated, authorities were going to perform “limited security checks” at Chicago’s public transit systems.
But the report caveated that there was “no specific, credible threat."
“We remain concerned that domestic extremists could be motivated to disrupt or attack the marathon in an effort to bring attention to their respective causes,” the report said.
During the marathon, the number of undercover officers will be beefed up, police said, and more patrols will be doled out to respective professional football and baseball games taking place in town.
"There is a great team here that understands events, and there is a great relationship between the event producers and Chicago police and federal agencies so we share best practices," Chicago Marathon Race Director Carey Pinkowski told Chicago’s WLS station.
Professor Robert Pape, director of projects on security and threats at the University of Chicago, suggested to WLS that the public often plays a critical role in helping authorities thwart attacks.
"Security comes in layers,” he said. “It comes in improving the security of the people in the city of Chicago. And that is in fact what you're observing in the last few weeks.”
ABC News' Josh Margolin and Christopher Donato contributed to this report.