KVOA TV, the NBC affiliate in Tucson, released a statement saying that the only viewers who were able to see the material were those who receive the channel through Comcast cable.

Comcast issued a brief statement saying the company was "mortified" by the interruption.

"Our initial investigation suggests this was an isolated malicious act," Jennifer Khoury, Comcast's vice president for corporate communications, said. "We are conducting a thorough investigation to determine how this happened."

The company says only customers in the Tucson area receiving the standard definition feed - not high definition - were affected.

Comcast has some 80,000 customers in unincorporated portions of Pima County, Marana and Oro Valley, but a company spokeswoman, Kelle Maslyn, declined to say how many standard definition customers there are or how many of those customers may have been watching the game.

KVOA TV said it supported Comcast's effort to find out what occurred. President and general manager Gary Nielsen said its investigation showed the signal left the station with no interruptions or inappropriate material.

"We ask Comcast to provide a full documentation for our viewers who are owed an explanation," he said.

The KVOA statement said the station was dismayed and disappointed that some Comcast customers and their families were subjected to the material.

"When the NBC feed of the Super Bowl was transmitted from KVOA to local cable providers and through over-the-air antennas, there was no pornographic material. KVOA will continue to investigate what happened to our clean signal and make sure our viewers get answers," Nielsen said in the statement.

Comcast spokeswoman Tracy Baumgartner confirmed that the company's standard feed was interrupted during the Super Bowl, although she said its high definition feed was not.

Tucson media outlets reported that they received calls from irate viewers about the pornographic material, which aired just after the Arizona Cardinals' Larry Fitzgerald scored on a long touchdown reception during the final minutes of the game.

Joel Hilander of Tucson told The Associated Press that he and his young children saw the clip.

"I couldn't believe it. And I couldn't believe that my children were watching it either," Hilander said.

In Washington, Federal Communications Commission spokesman David Fiske said he was not aware of any complaints having been filed with the FCC as of Monday afternoon.

"At this point we just have no information," he said. If the agency receives complaints, review procedures will be followed.

"Every case concerning enforcement or indecency is fact-specific," he said, and added, "we can't ever speculate."

Khoury also said it was too soon to discuss a number of unanswered issues, ranging from how and why the incident occurred to what the source was and how the company's security system was breached.

Other questions include whether the interruption could have emanated from any broadcast provided for on-demand customers and whether any employees of the company might face discipline, depending on the investigation's outcome.

Fiske could not say whether the FCC potentially could impose a fine or other disciplinary action.

"It depends on what the facts are," he said.