State prosecutors have urged Spain's National Court to investigate four alleged former Nazi concentration camp guards and decide whether to seek their extradition from the United States over the deaths of Spanish citizens in the camps, news reports said Monday. The Europa Press news agency said the prosecutors office at the court announced it was backing a case petition brought last month by Brussels-based rights organization Equipo Nizkor on behalf of victims' relatives. The suspects are John Demjanjuk - an 88-year-old retired auto worker in Ohio - Anton Tittjung, Josias Kumpf and Johann Leprich. Equipo Nizkor has said the US has been trying for years to deport all four for lying about their Nazi pasts on their immigration papers, but that no country had been willing to take them. The prosecutors' petition is a non-binding recommendation. The court's judges will now decide whether to accept the case for study and consider filing charges. A decision could take months. No one was available at the prosecutors' office for comment late Monday. The Simon Wiesenthal Center in Jerusalem, which worked with Equipo Nizkor to prepare the suit, has called the petition hugely important. Demjanjuk, tied up in legal battles over his wartime past for more than three decades, is No. 2 on the center's "most wanted" list of Nazi war criminals - below only the brutal SS doctor Aribert Heim. Europa Press quoted unidentified court officials as saying they hoped the case could be expanded to include Heim. Demjanjuk's son, John. Jr., told The Associated Press last month that his father was innocent of "the same old desperate charges." The suit was presented under Spain's principle of universal jurisdiction. This states that war crimes, crimes against humanity, terrorism, torture and other heinous offenses can be prosecuted in Spain, even if they have been committed abroad. Spanish judges have used the legal principle to go after the late Chilean dictator Augusto Pinochet, al-Qaida leader Osama bin Laden and figures from the Argentine 'dirty war' of the 1970s and 80s, among other people, albeit with very limited success. Equipo Nizkor said the fact that thousands of Spanish citizens died in Nazi camps where the four suspects allegedly worked is another reason for Spain's National Court to charge them. The group's complaint says the suspects served as guards in the concentration camps at Flossenberg and Sachsenhausen in Germany, and Mauthausen in Nazi-occupied Austria. Demjanjuk was born in Ukraine, Leprich in Romania, Kumpf in Serbia and Tittjung in what is now Croatia. Leprich, 82, has lived in the Detroit, Michigan, area, while Kumpf, 83, resides in Racine, Wisconsin, and 83-year-old Tittjung's listed address is in Kewaunee, Wisconsin.