Less than two hours after Amanda Knox was acquitted of murder, the 24-year old Seattle woman was released from prison without fanfare and is expected to arrive back on U.S. soil Tuesday.

Knox was seen leaving the Cappane prison at just after 5 p.m. EST in a Mercedes sedan with tinted windows, CNN reported.

That was her private escort out of here, CNN's Paula Newton said. I did get a very short glimpse of her. It was her.

A man identified as a friend of Knox's told CNN that her passport is valid (the passport was believed to have expired while she was in prison) and that Knox is expected to fly home to Seattle on Tuesday.

The U.S. State Department had earlier Monday offered a statement of support to Knox.

The United States appreciates the careful consideration of this matter within the Italian judicial system, said Victoria Nuland, a spokeswoman for the U.S.State Department. Our embassy in Rome will continue to provide appropriate consular assistance to Ms. Knox and her family.

Shortly before Amanda's release, Meredith Kercher's family -- who was present when the appeal verdict was announced -- released a statement through a representative: We respect the decision of the judges but we do not understand how the decision of the first trial could be so radically overturned. We still trust the Italian judicial system and hope that the truth will eventually emerge.

Knox and Raffaele Sollecito were freed when the Italian appeals court overturned both of their guilty verdicts for murdering Knox's flatmate Kercher in 2007. Both were convicted in 2009 after a ten month long trial.

Knox was found guilty of defamation and was sentenced to a fine and time served.

When the verdict reversal was announced, Knox collapsed in tears, and moments later was shuffled from the court. Earlier Monday she had been reported to be playing guitar and singing religious songs in anticipation of a favorable ruling.

Knox delivered a heartfelt appeal earlier Monday in fluent Italian (though she barely spoke the language four years ago). Knox maintained her innocence, insisting again that she was not at the flat at the time of Kercher's murder, and claiming that if she had been, she might be a victim herself.

Shortly after the verdict was announced, Amanda's sister addressed the crowd: Some who were cheering in support, some who were shouting murderer!

We're thankful that the nightmare is over, Deanna Knox said. She has suffered for four years for a crime that she did not commit. We are thankful to the court for looking for the truth.

We now respectfully ask you to give her family the privacy to recover from this horrible ordeal.

Geoff Hill of CNN London has been tweeting updates to the court announcement, and in a recent tweet said that crowds were chasing Sollecito's lawyer through Perugia shouting 'shame shame.'

Later, Hill tweeted that the acquittal will go down as a truly astonishing miscarriage of justice.

Watch Amanda Knox react to the appeal verdict here: