Never mind President Barack Obama's inauguration address or what Michelle Obama was wearing at the ball. Was Beyonce lip-synching the US national anthem on Monday, or wasn't she?

The Grammy-winning singer remained silent on Tuesday amid a media storm over whether she was lip-synching, singing over her own pre-recorded track, or performing live when she delivered a flawless version of "The Star-Spangled Banner" to hundreds of thousands of people in Washington and millions watching on television.

A spokeswoman for the US Marine band first told US news outlets on Tuesday that the "Single Ladies" star "decided to go with the pre-recorded music at the last minute" and that, to the spokeswoman's knowledge, she was not actually singing the anthem.

But the US Marine band later backtracked, saying in a statement: "Regarding Ms. Knowles-Carter's vocal performance, no one in the Marine Band is in a position to assess whether it was live or pre-recorded."

The statement said the band and Beyonce, whose surname is Knowles-Carter, had no chance to rehearse together before Monday's inauguration "so it was determined that a live performance by the band was ill-advised for such a high-profile event.

"Each piece of music scheduled for performance in the Inauguration is pre-recorded for use in case of freezing temperatures, equipment failure, or extenuating circumstances," the Marine Band added.

Beyonce, 31, was giving her first major public performance since giving birth to a baby with husband, rapper Jay-Z, in January 2012. On Sunday, she posted on Instagram photo of herself in a recording studio holding the sheet music for "The Star-Spangled Banner."

Her representatives did not return calls for comment on Tuesday. Kelly Clarkson and James Taylor, who also performed at the inauguration ceremony, both sang live, their publicists said.

Whatever Beyonce's choices on Monday, she was not the first artist cause a stir on such occasions.

Classical musicians Yo-Yo Ma, Itzhak Perlman and two others played along to a pre-recorded tape at Obama's 2009 inauguration because the cold and wind on the Washington Mall raised the potential of broken strings and sharp notes.

Madonna lip-synched her way through her 2012 Super Bowl half-time performance last year, as did the late Whitney Houston in her 1991 Super Bowl rendition of the national anthem. Singing to pre-recorded tracks has become widespread in the pop music industry

The lip-synching question made headlines around the world and "Beyonce" was among the top Facebook conversations on Monday, according to the social networking site.

Fans were divided. "I enjoyed the performance and do not care whether it was lip-synched or not - it was a beautiful rendition, with some originality, of a song we have all heard so many times," wrote LeeAnne24 on the Washington Post comment board.

Twitter user hiphopdancerJen was disappointed. "There's honestly no reason for Beyonce to lip-sync... Especially the national anthem. I may despise most of her music, but she has a voice."

Beyonce is due to take the spotlight again next month - this time at the February 3 Super Bowl half-time show.