The pop star, 31, wowed the crowd of about 800,000 people during Monday's presidential Inauguration with her powerful rendition of the "Star-Spangled Banner."
But it wasn't a live performance, according to a Marine Corps Band spokesperson, who says the band wasn't playing and Beyoncé was lip-syncing to her own voice.
"We all know Beyoncé can sing," Kristin Dubois, Master Sgt. of the U.S. Marine Corps Band, told ABC News on Tuesday. "We all know the Marine Corps Band can play. We do not know why she decided to go with the pre-recorded music at the last minute."
Dubois adds that the band performed live to accompany the other acts, including Kelly Clarkson, but was specifically asked not to play during Beyoncé's performance. PEOPLE has confirmed that Clarkson indeed performed live.
However, the story isn't so cut-and-dried. "There was no opportunity for Ms. Knowles-Carter to rehearse with the Marine Band before the Inauguration so it was determined that a live performance by the band was ill-advised for such a high-profile event," Capt. Gregory A. Wolf, media officer from the Pentagon, said in a statement Tuesday afternoon.
Regarding Beyoncé's performance, Wolf said, "No one in the Marine Band is in a position to assess whether it was live or pre-recorded."
Wolf says that as a regular practice, each piece of music scheduled for performance during the Inauguration is pre-recorded in case it's needed for extenuating circumstances such as freezing temperatures or equipment failure.
In video of Beyoncé's performance, it's unclear if she was singing live along with the pre-recorded track.
A rep for the star has not returned a request for comment.