Teams of federal agents could be prowling airport perimeters next year as congressional investigators scrutinize federal efforts to safeguard planes, tarmacs and runways.

The federal investigation will focus on perimeter security technology, background checks, training and planning -- all topics in a 2004 report critical of the Transportation Security Administration.

"We're basically looking to see where TSA stands on the issues we raised in our previous report," says Norman Rabkin, managing director of the Homeland security and justice team at the Government Accounting Office.

The GAO inquiry could include a special unit snooping undercover on airport perimeters in search of security weaknesses, Rabkin adds.

Former federal investigators and pilots groups say perimeter security is among several deep flaws in the nation's airport security system.

TSA officials say such charges are off base.

The agency has met the mandates set by congressional investigators in the 2004 GAO report, TSA spokeswoman Sari Koshetz says. Those include requiring fingerprint-based background checks and security training for all airport workers and security programs from all airport vendors.

Further, the TSA and Federal Aviation Administration have helped pay for the construction of perimeter access roads, the installation of electronic surveillance systems and security fences at airports around the country, Koshetz adds. She cites $16 million in federal grants for state-of-the art perimeter control surveillance and ground radar systems and exit lane controls.

The request for the GAO to revisit perimeter security came from incoming Democratic committee and subcommittee chairmen. The GAO expects to start work early next year and hopes to release a report by the end of the year, Rabkin says.

Among the points TSA critics want the GAO to consider is what they call an absence of accountability for perimeter security.

Perimeter security falls under TSA oversight, but is largely left to local agencies. TSA must approve a local security plan, but authorities such as port authority police carry out the daily task of guarding the perimeters.