The Transportation Security Administration said Wednesday it is screening more passengers at airport gates, but not because of any specific threat.

Gate screening - which can involve anything from identification checks to hand-wand metal detectors - was implemented after Sept. 11 as an additional layer of security. It all but disappeared in 2003, when the TSA began screening all checked bags.

Although the TSA follows a "risk-based approach" when adding security measures, TSA spokeswoman Lara Uselding told the Associated Press that the move to restore random gate checks developed "as the agency evolved," not because of a specific threat. The TSA collects intelligence from the FBI as well as state, local and national government agencies when forming new procedures.

The gate checks for passengers follow the establishment of an employee security program in 2007, which included random screenings. The checks aim to prevent weapons or other contraband being passed from an employee to a passenger before boarding, among other risks.

"Gate screening is particularly effective at addressing insider threats and serves as a random and unpredictable security layer that, like all TSAs security measures, was developed using a risk-based approach," Uselding said. "In support of TSAs overall security strategy, the frequency of gate screening has increased and may occur unannounced at gate areas anytime."

Uselding said letters were sent to airlines last week informing them of the security change, although the new gate screening procedures have been in place for a couple of months. She would not say how many passengers or employees have been randomly stopped at gates, or how that figure has changed in recent years.

Because passengers at a certain gate are screened does not mean there is a specific threat to a particular plane, Uselding said.

She said signs at gates inform passengers that screening may occur. Uselding acknowledged that some passengers may see additional screening after a comprehensive search at a security checkpoint as unnecessary or annoying.

"Everything we do here at TSA is for a reason, it's not made to make travelers' lives a hassle," she said.