Prosecutor Javier Monasterios told reporters that authorities were investigating others in the case.
Ostreicher told The Associated Press that prosecutors told him there would be more arrests and that 11 people "who work for the government are under suspicion" for allegedly abuses of authority in his case.
"I'm very concerned that now that the story is finally going to break that, with 11 government officials involved in corruption, some officials are going to think that what better way to get rid of me but to kill me," Ostreicher said from a clinic in the eastern city of Santa Cruz.
"So I have concern right now about not only my physical health but my safety," added Ostreicher, 54.
Ostreicher has been treated at the clinic for malnutrition from a liquids-only hunger strike he mounted to protest his incarceration.
U.S. diplomats and New Jersey congressman Christopher Smith have also been visiting Ostreicher, an orthodox Jew from Brooklyn, N.Y., and interceding on his behalf.
The Associated Press has repeatedly questioned senior Bolivian officials about the case since last year, including its foreign minister and interior minister. The officials had said only that they would look into it.
Under Bolivian law, suspects may not be jailed for more than 18 months without charge.
Earlier this year, the regional director of DIRCABI, the state agency in charge of seized assets, was fired over the illegal sale of Ostreicher's rice.
The American says he went to Bolivia to salvage a rice-growing investment after the local manager, whom he described as a Colombian con artist, defrauded investors and planted some of their rice on land owned by the brother of a Brazilian drug trafficker.
Prosecutors initially alleged that the $25 million invested in the rice venture was obtained illegally.
Ostreicher said he suspected from the moment of his arrest that Bolivian officials saw in him a golden opportunity to strip of all their assets a pair of foreign investors who had no clue how perilous Bolivian agribusiness would prove for them.