Former Portuguese Prime Minister Jose Socrates is back in court for more questioning by a judge about suspected corruption, money-laundering and tax fraud.

Socrates arrived at the Lisbon court in a police car Monday after spending a third straight night in jail.

The judge is conducting a preliminary hearing, after which he must rule whether Socrates should be released or kept in custody pending a trial.

Socrates was Portugal's center-left Socialist prime minister from 2005 to 2011. He was detained by police late Friday. Authorities said he and three others are suspected of crimes.

Officials refused to provide details of the case. In Portugal, a judicial secrecy law forbids the disclosure of information from ongoing investigations.