The Federal Communications Commission repeatedly defended its decision to grant special permission to a company to set up a controversial cellular network using satellites, despite a growing chorus of warnings this year about the system’s safety, according to letters and files distributed by the agency Wednesday.

The trove of hundreds of documents shows widening concern by lawmakers, federal agencies and consumers over whether the satellite technology owned by the firm, called LightSquared, would interfere with GPS systems and put airplanes in harm’s way. These officials also questioned whether the FCC had thoroughly tested the system.

The release, which was in response to a Freedom of Information Act request by several media outlets, largely cull from the public record and did not include any of the internal deliberations that led FCC Chairman Julius Genachowski to bypass a vote by his own commission and allow LightSquared to move forward with its plans.

Sen. Charles E. Grassley of Iowa, the ranking Republican on the Judiciary Committee, on Wednesday criticized the FCC for delaying the release of private documents from the chairman’s office.

“This holiday week document dump and the fact that these documents are already publicly available is a continuation of the FCC’s pattern of hiding any actual information regarding the LightSquared waiver,” Grassley said in a statement. “This is an agency with a very serious transparency problem. The FCC needs to stop playing games and make itself accountable to Congress, the media and the American people.”

FCC spokeswoman Tammy Sun declined to comment on Grassley’s concerns or on the agency’s LightSquared decision. The agency has told Grassley that the Judiciary Committee does not have the authority to demand documents. And the FCC has noted that it granted its special permission in January to LightSquared on the condition that the company solve any interference problems.

Within the FCC, an official who spoke on the condition of anonymity because the LightSquared proceeding is still active, said the issue should have gone to a full commission vote and that it was presented to other members as though it were irreversible.

The controversy over LightSquared comes as the agency is facing efforts by Republicans to reform the commission. The GOP-led House communications subcommittee approved a bill this month that would force the FCC to make information more transparent and enact timelines to shorten merger reviews. Rep. Fred Upton (R-Mich.) said the full committee would vote on the measure by the end of the year.

Grassley has threatened to hold up the confirmation of President Obama’s nominees Jessica Rosenworcel and Ajit Varadaraj Pai for the FCC’s five-member commission until Genachowski responds to his requests for more information on LightSquared. He has said the FCC appeared to “fast-track” the venture’s plans. LightSquared is backed by billionaire hedge fund investor Philip Falcone, a Republican donor who has been giving large sums to Democrats in recent years.

Dozens of other lawmakers have expressed similar concerns as Grassley’s. In a letter sent May 20, Sen. Mike Johanns (R-Neb.) asked why the. FCC granted the waiver without first testing the network for interference. He said he was “concerned” that the Department of Transportation and Department of Defense “viewed the FCC’s work on the license as inadequate.”

In responses to Johanns and other lawmakers, Genachowski said the agency would not allow LightSquared to turn on its network unless GPS interference issues were resolved. In a Sept. 15 letter to Rep. Loretta Sanchez of California, the ranking Democrat on the strategic forces subcommittee of the Armed Services Committee, Genachowski went into greater detail.

He said proposals do not have to go to a full vote when “a waiver will serve the public interest and good cause has been shown.”

“The commission’s rules permit decisions to be made on delegated authority to ensure the timely consideration of pending requests to support a robust and active telecommunications industry and to ensure that the agency is not placing unnecessary barriers in front of commercial activity, private investment and job creation,” Genachowski wrote.