A Chicago-bound flight was delayed for hours Thursday after a mock improvised explosive device (IED) was discovered inside of a passenger's suitcase at Toronto Pearson International Airport, CTV News reported.

United Airlines Flight 547 was forced to wait for several hours on the tarmac after customs agents made the discovery during an inspection at the airport's pre-clearance area, a U.S. Customs and Border Protection spokesperson said in a statement issued Thursday.

The CBP officers immediately alerted the Canadian Air Transport Security Authority (CATSA) who swabbed the mock IED for explosives with a negative result, the statement confirmed.

An unidentified 58-year-old American man was arrested in connection with the incident.

"For the safety of travellers within the pre-clearance facility (PCF), CBP stopped all traveller processing while the mock IED was tested," the CBP statement continued. "CBP conducted a joint inspection of the aircraft, rescreening all travellers and baggage."

Normal operations at the airport have resumed and the flight has been cleared. However, an investigation into the incident is ongoing.

According to passenger Dal Gemmell, passengers aboard Flight 547 to Chicago's O'Hare International Airport were forced to wait on the plane for four hours before exiting to an isolation area.

"Throughout my career, I have always been very truthful and honest about situations like these, and I’m going to just do that right now," the pilot was heard saying over the plane's intercom via CTV. "The U.S. Customs has revoked the pre-clearance privileges for you to enter the United States. Therefore, we cannot leave at this time."

Passengers aboard Flight 547 were originally informed that the lengthy delay was due to poor weather conditions in Chicago.

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