Swag given to attendees of the South By Southwest festival set off airport security alarms Wednesday, leaving passengers complaining of long delays as they tried to head home.

Jason Zielinski, an Austin-Bergstrom International Airport spokesman, said that a particular type of ink on some item was thought to have made it difficult to scan baggage with X-ray machines, forcing officials to individually screen bags.

Zielinski said he didn’t know the exact cause of the problem, but said he’d heard it blamed on festival promotional items, including stickers, a free magazine “or any combination of things.”

He referred all questions to the Transportation Security Administration, adding “it’s out of our lane.”

TSA also wouldn’t say what was causing the problem or exactly how it was detected, citing security concerns. In a statement, the agency said only that “if an item in a bag is unable to be clearly viewed as part of the screening process, or if an item alarms, additional screening may be needed before the bag is cleared.”

“In this case, TSA suggests that bulky conference promotional materials be packed in carry-on bags and placed in a bin at the security checkpoint for faster screening,” the statement said.

Attendees picking up South By Southwest admittance badges were given a series of cloth bags with colorful logos that contained bulky, glossy event programs. It was unclear, though, if such materials were the culprit since the festival is awash in outside swag and small promotional trinkets, with everything from visors and umbrellas to sun screen, bottle openers and lip balm being given away by advertisers all over town.

A South By Southwest spokeswoman did not return an email seeking comment.

Zielinski said it wasn’t clear how many flights were affected. Still, scores of travelers used Twitter to blame festival magazines, stickers or brochures for extra baggage screenings that delayed their flights.

University of Southern California journalism professor Robert Hernandez was aboard an American Airlines flight from Austin to Los Angeles when an unusual pre-takeoff announcement caught his attention.

“Our flight is delayed because a free magazine given out at #SXSW is registering as a bomb. And each bag must be inspected,” he tweeted. “I’m serious.”

Hernandez said the pilot didn’t say which magazine, only that something in the ink or paper was registering as problematic for security scanners.

South by Southwest’s interactive portion ended Tuesday, but its film and music festivals remain in full swing. The conference showcases up-and-coming acts but also established talent like Lady Gaga. During 2013’s festivities, more than 25,000 people saw 2,278 acts.

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Photo Credit: Baggage carts at Austin-Bergstrom International Airport. David Poe / Flickr