The Transportation Security Administration came under heavy fire this week for inadvertently posting its "sensitive security" aviation screening manual online.

The TSA quickly pulled the manual off the web -- and tried to soften the breach by calling the manual outdated -- but the leak sparked sharp criticism from lawmakers and those in the industry who fear the agency may have provided terrorists with valuable information they could use to circumvent national air travel security measures.

The manual remains available online at several different sites.

"The Transportation Security Administration recognizes an outdated, unclassified version of a Standard Operating Procedures document was improperly posted by the agency to the Federal Business Opportunities website wherein redacted information was not properly protected," the TSA said in a statement.

"Once we were made aware, it was immediately taken down," the TSA said. "There have been six newer versions of the procedures since the version posted was approved."

Lawmakers still want to know how the manual wound up on the Internet in the first place.

Chairman of the Senate Judiciary Committee Patrick Leahy (D-Vt.) asked during a previously scheduled oversight hearing on DHS security issues yesterday: "Who should be held accountable?"

Speaking at that hearing, Homeland Security Secretary Janet Napolitano said the manual was posted online by a contractor, who had reported to TSA supervisors.

"It was an out-of-date manual," Napolitano said. Making it public, she said, poses no security risks for air travelers, she added.

Still, she said, "The posting of it did not meet our own standards of what should be available on the net."

While the DHS has already disciplined the appropriate employees for their involvement in the incident, Napolitano said she has asked the DHS Inspector General's office to investigate.