ET has obtained court records released Friday indicating that Mayumi Heene told the police she and her husband Richard knew their little boy Falcon, who was feared to have floated off in a balloon device, was safe at home all along.

The search warrant affidavit says Mayumi told investigators that the incident was a publicity stunt designed to enhance the family's marketability to the press.

The document says she and Richard came up with the alleged ruse two weeks earlier, and the balloon device "was specifically made to carry out this hoax. ... she and Richard had instructed their three children to lie to authorities as well as the media regarding this hoax."

Richard Heene's lawyer responded that "allegations are cheap" and he's yet to see the evidence, says the Associated Press. Mayumi's lawyer didn't immediately respond to messages left for him.

Investigators say they'll suggest criminal charges against the parents.