HOUSTON -- Air traffic was grounded for more than an hour at Houston's George Bush Intercontinental Airport Thursday evening after two women passed through a security checkpoint without being screened.

Authorities were unable to find the two unidentified women, who slipped through a metal detector at Terminal C that was not being used about 6:45 p.m., said Roger Smith, spokesman for the Houston airport system.

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Airport Delays

Bush Intercontinental Airport

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"We really don't know if they intentionally made a security breach," he said. "What we do know is that they went through. It could have been because of confusion."

Travelers waiting in Terminal C were evacuated about 15 minutes later after airport officials observed the incident on the airport's video surveillance system. K-9 units were called in to search the terminal.

The evacuation affected 11 flights and about 1,100 passengers, who were screened a second time before reentering the airport.

It prompted a "gate hold" in which no flights took off, and passengers on arriving flights were not allowed to deplane.

Using the process of elimination, all areas of the airport were searched, but the women were not found. Smith said nothing suspicious was found, and all terminals reopened by 10 p.m.

"We did a thorough search of every sector of the four terminals, and they didn't turn up anywhere. We're not actively searching for them," Smith said. "We have determined there's no danger."

Terminal A stayed open during the incident since it is not connected to the other terminals.