A former treasurer for Spain’s governing People’s Party was sent to jail without bail on Thursday as the High Court continues a pretrial investigation into corruption charges against him. Judge Pablo Ruz said that the former official, Luis Bárcenas, who worked for the People’s Party for almost three decades, mostly in the accounting department, had failed to explain the origin of up to $61 million held in Swiss bank accounts. The judge said Mr. Bárcenas was a flight risk and could also interfere with witnesses or destroy evidence. Mr. Bárcenas said that he was innocent of the charges against him and that his money came from legitimate business activities.