Washington (CNN) -- Just days after serving subpoenas to two travel bloggers, the Transportation Security Administration withdrew the subpoenas late Thursday, saying its investigation into how the bloggers received a sensitive security directive "is nearing a successful conclusion."
With little explanation, the TSA withdrew subpoenas of bloggers Steve Frischling and Christopher Elliott seeking information on how they obtained a December 25 security directive. The directive, which had been sent to every airline and airport in the United States, ordered precautions after the failed terrorist attack on Northwest Airlines Flight 253.
The TSA acknowledged in a previous statement that it was investigating the leak and publication of the document, saying, "Security directives are not for public disclosure."
Frischling, founder of the Travel Strategist blog, said TSA agents came to his Connecticut home Tuesday evening to question him about his source, leaving for a brief time to go to Wal-Mart to buy a hard drive in a failed effort to copy his hard drive that night.
The agents returned Wednesday morning and left with his laptop computer, Frischling said. Frischling said the agents threatened to call a client -- an airline -- and have them sever his contract, saying he was a security threat.
Frischling said that he does not know who sent him the security directive and that the laptop did not include any identifying information about his source.
Frischling said he was contacted Thursday evening by TSA Deputy Chief Counsel John Drennan, who told him the agency was "no longer investigating how I came into the document." Drennan "apologized on the heavy-handed tactics the TSA agents took," Frischling said.
Blogger Christopher Elliott posted on his blog -- www.elliott.org -- a letter from the TSA withdrawing the subpoena, saying it was "no longer necessary."
Elliott wrote that he had "signaled his intention" to fight the subpoena in court.
"Needless to say, I'm delighted by this turn of events," Elliott wrote.
Elliott thanked his lawyer and several journalism and privacy organizations for coming to his assistance, as well as Department of Homeland Security Special Agent Robert Flaherty for being "a true professional."
In a statement Friday, the the agency wrote, "TSA takes any breach in security very seriously. In light of the posting of sensitive security information on the web, TSA sought to identify where the information came from. The investigation is nearing a successful conclusion and the subpoenas are no longer in effect."
The TSA security directive at issue outlined procedures to increase security, including requiring airlines to conduct physical searches of passengers during certain international flights and prohibiting passengers from keeping pillows and blankets on their laps. Portions of the directive have been amended since it was issued, officials have said.