By John Marino SAN JUAN, Oct 30 (Reuters) - Federal and local authorities on Tuesday arrested 29 people, including two past presidents of the Puerto Rico Board of Medical Examiners, bringing to 112 the number of people detained in the U.S. territory in an ongoing medical fraud probe. Most of those arrested were doctors who authorities said had failed licensing tests but were still fraudulently granted passing grades and medical licenses after paying bribes or bestowing favors. Among the defendants were former Board presidents Margarita Perocier-Aguirre, who served from October 2000 to January 2002, and Rafael Jimenez-Mendez, who held the post in 2002. Federal prosecutors accuse the doctors of changing test results on behalf of medical students who had failed exams in exchange for "money, things of value and sometimes in exchange for political favors." Bribes of up to $6,000 were paid to receive a fake passing score, according to authorities. Those arrested were charged with mail fraud, honest service fraud and mail fraud conspiracy. They face penalties of up to 20 years in jail and fines of up to $250,000 if convicted. "This conspiracy was going on for many years. It is time for Puerto Ricans to regain their faith in the medical community, and today we have taken a big step in that direction," said U.S. Attorney Rosa Emilia Rodriguez-Velez in a news conference. In August, federal and local authorities arrested 89 doctors and two officials from the nine-member Board of Medical Examiners on charges stemming from forged test results between 2001 and 2005. Besides testing and licensing local doctors, the board is also in charge of probing complaints against local doctors. A proposed law change filed in the Caribbean territory's legislature would replace local licensing exams with the U.S. Medical Licensing Exam. The move has stirred debate because the test is only available in English.