Sandaza was duped into admitting he only joined the club for the money by a man called 'Tommy' who posed as a US-based agent but is well known in Glasgow as a regular caller to various radio station phone-ins.
"Francisco will not return to the club while the investigation is under way," Rangers said in a statement.
"The club, Francisco and his agent have had discussions and manager Ally McCoist also spoke with the player, who did not take part in today's training session.
"Rangers regard this is an extremely serious issue but there will be no further comment until the inquiry, which could take a week, has been completed."
The man, apparently a cabbie and a Celtic supporter, somehow obtained the forward’s phone number, pretending he was Jim McGonagle, a fictional MLS agent looking to sign European players to American clubs.
Sandaza, who joined Rangers from St Johnstone in the summer, has struggled in Scotland’s Third Division, admitting that he injury had taken its toll on his season and he would be keen on a move to America.
During the recorded conversation, Sandaza admits that the weather and standard of football are not good, lifts the lid on his £4,500 per-week wages, and says he would move to MLS without blinking if he was offered “a bit more money”.
“I only signed for the money,” he said. “I didn’t sign for the level.”
Sandaza values himself at £500,000, and added he would like to see any proposed contract before Rangers are informed:
“First if you have something official for a club that wants to pay money for me, show me the contract, and if everything is okay I will give you the okay to speak with Rangers.
“If I don’t see anything official first I don’t want any trouble with Rangers, maybe the press finds out.”
Rangers fans calling for his head should take note that the 28-year-old also called the club and the fans “amazing”, while he refuses to criticise manager Ally McCoist, saying he will not talk about personal matters with someone he has not met.
McCoist is also unsure what the future holds for Sandaza, who signed a three-year deal in August after netting 18 times in the Scottish Premier League last term.
"We will have to wait to see what the investigation unfolds," said McCoist.
'Tommy' also duped Rangers former owner Craig White with a similar 'hoax' phone call last year when he persuaded Whyte that he was a Rangers fan from the US and keen to buy a stake in the 'oldco' Rangers before they were liquidated and forced to restart life in the Scottish Third Division.