Bolivia's attorney general is seeking to put three former presidents on trial for alleged irregularities in contracts with foreign oil companies.
Mr Sanchez de Lozada also faces genocide charges
Carlos Mesa, Gonzalo Sanchez de Lozada and Jorge Quiroga are accused of making deals that violated the constitution.
This means Bolivia's last four presidents could all face prosecution.
Last week, the attorney general asked for permission to try Eduardo Rodriguez, the interim president who served before December's election.
Mr Rodriguez is accused of submission to a foreign power in a case relating to the decommissioning of Bolivian missiles in the United States.
He denies any wrongdoing.
The allegations against the four former presidents have been presented to the Supreme Court. It must decide whether to pass them on to Congress, which in turn must authorise any trial.
The ruling MAS party holds a majority in Congress. The backing of two-thirds of all deputies and senators is required for a trial.
Opposition parties linked to two of the presidents have dismissed the move as politically motivated.
After looking at deals reached with foreign oil firms between 1993 and 2003, Attorney-General Pedro Gareca said he had found illegalities in:
- 39 contracts signed by Gonzalo Sanchez de Lozada, who governed from 1993 to 1997 and 2002 to 2003.
- Four contracts agreed by Jorge Quiroga, who served in 2002
- One deal signed by Carlos Mesa who governed between 2003 and 2005.
Mr Sanchez de Lozada - who now lives in the US - has also been formally charged with genocide over the deaths of 60 people killed during a wave of social unrest.
The allegations against Mr Rodriguez - interim president from 2005 to 2006 - relate to the destruction in the US last year of some 30 missiles owned by Bolivia.
President Evo Morales described their destruction as a US plot to weaken Bolivian defences.