A 9-year-old boy passed through security at the Minneapolis/St. Paul International Airport and flew on a Delta Air Lines plane to Las Vegas without a boarding pass, authorities said on Sunday.

It was not immediately clear why the child sneaked onto the flight on Thursday, but his action raised questions about airport and airline security.

Despite numerous checkpoints and gate agents, officials at Minneapolis/St. Paul International Airport say a 9-year-old was somehow able to sneak through security and onto a Delta flight headed to Las Vegas.

"At this point, this is a Delta and TSA issue," said airport spokesperson Pat Hogan. "This is a rare incident."

The security mishap occurred Thursday on Delta Flight 1651. It wasn't until the plane landed in Las Vegas that the boy was stopped and questioned.

MSP officials say they've reviewed security footage and at this point do not believe he was carrying a boarding pass.

In a statement sent to KARE-11, Delta officials said, "We are investigating the incident and cooperating with the agencies involved." Authorities with the TSA released a similar statement.

"It's crazy," said Ryan Linderman, while passing through MSP airport Saturday. "I have an 8-year-old and that freaks me out."

Authorities believe the 9-year-old boy is a runaway from the Twin Cities.