A 9-year-old runaway went through security, boarded a plane at the Minneapolis-St. Paul International Airport without a ticket and flew to Las Vegas, an airport spokesman said Sunday.

Security officials screened the Minneapolis boy at the airport shortly after 10:30 a.m. Thursday after he arrived via light rail, Metropolitan Airports Commission spokesman Patrick Hogan said. The boy then boarded a Delta flight that left for Las Vegas at 11:15 a.m.

The flight was not full, Hogan said, and the flight crew became suspicious midflight because the boy was not on their list of unattended minors. The crew contacted Las Vegas police, who met them upon landing and transferred the boy to child protection services, Hogan said.

"It's hard to piece anything together from his stories why he got on the flight and went to Las Vegas," Hogan said.

Minneapolis police Sgt. Bill Palmer said officers talked to the family after Las Vegas police contacted them. A family member told police the boy ran away and was last seen earlier Thursday.

The boy had been at the airport on Wednesday as well, Hogan said. Video shows him grabbing a bag from the carousel and ordering lunch at a restaurant outside of the security checkpoints.

He ate and then told the server he had to use the bathroom. He left the bag and never returned to pay, Hogan said. Airport officials returned the bag to its owner.

Delta and the Transportation Security Administration said in separate statements that they were investigating.

Hennepin County Child Protection Services also was looking into it, Palmer said. County spokeswoman Carolyn Marinan said Sunday she couldn't confirm or deny the agency's involvement because the case involves a juvenile and data privacy issues.

The boy was expected to return to the Twin Cities, but Hogan didn't know Sunday if that had happened yet.