Los Angeles  - Five years after singer Janet Jackson caused a Super Bowl controversy by exposing her breast in the half-time show, a much more shocking malfunction popped up for some fans watching the biggest game of the year.

According to reports Monday, thousands of viewers were subjected to a 30-second pornographic video clip as Sunday's NFL title game reached its climax.

Viewers in Tucson, Arizona, were celebrating a touchdown by their team, the Arizona Cardinals, with less than three minutes to go in the game when the broadcast dissolved into a scene featuring full frontal male nudity from the adult channel Club Jenna.

The offensive images were only transmitted to subscribers of the Comcast cable company, many of whom seemed to think that the segment was just another ad until it featured nudity.

"I just figured it was another commercial. ... Then he did his little dance with everything hanging out," Cora King of Marana, Arizona, told the Arizona Star newspaper.

Officials at Comcast said they were "mortified" by the incident and were working on finding the cause of glitch.

"Our internal investigation suggests this was an isolated malicious act," said Comcast spokeswoman Kelle Maslyn. "We are conducting a thorough investigation to determine how this happened." (dpa)