People wait outside Houston's William P. Hobby Airport after a toy grenade in a passenger's bag forced the shutdown of a security checkpoint, inconveniencing hundreds of people catching early-morning flights. Picture: John L. Mone/AP

Houston — A Boy Scout who packed a toy grenade in his carry-on bag caused the shutdown of a security checkpoint at Houston's William P. Hobby Airport Thursday morning, just a day after the international terminal of the city's other major airport was evacuated due to a bomb scare.

Houston Airport System spokesman Bill Begley said people were allowed to approach the checkpoint again after authorities determined that the suspicious item spotted by a Transportation Security Administration agent was a "novelty grenade." It's not clear why the 17-year-old had the item in his bag.

Houston police said the state won't charge the teen but that he could face a federal fine.

Hobby Airport is a hub for Southwest Airlines and Begley said more than 15 Southwest flights were delayed. 

An Associated Press journalist was in the line when a TSA agent raised the alarm at about 4:35 a.m., forcing hundreds of people to move away from the immediate area on both sides of the security checkpoint.

"My wife and I were waiting to drop our bags into the X-ray machine and go through the detector, and I heard a TSA agent scream 'Shut it down, shut it down, shut it down!' Everyone was looking around, confused, and people were ordered to 'Clear out now!'" the AP's John L. Mone said.

The explosives scare occurred only a day after police detained "an impatient passenger" who made comments about explosives in a bag at Houston's Bush Intercontinental Airport. Begley said that unidentified passenger's "inappropriate comment" prompted a bomb squad to close the international terminal for nearly an hour.

The episode created a backlog of at least a thousand people waiting to go through security.

AP