Rome , Italy ( CNN ) -- The oldest known image of the apostles Andrew and John have been discovered in catacombs under the city of Rome , dating back to the 4th century AD , archaeologists announced Tuesday . The paintings were found in the same location where the oldest known painting of St. Paul was discovered last year , the Pontifical Commission for Sacred Archeology said Tuesday . They are part of a group of paintings around an image of Jesus as the Good Shepherd on the ceiling of what is thought to have been a Roman noblewoman 's tomb , experts said . A painting of St. Peter makes up the fourth member of the group , but older images of him are thought to exist , Vatican experts said . Their inclusion in the tomb shows the aristocrats were among the last Romans to convert to Christianity , archaeologist Fabrizio Bisconti said . The Roman matron must have been very rich , he said , as the colors and richness of the decoration show . The images of the apostles ' heads and shoulders against a deep red background were uncovered after two years of work , Vatican experts said . Archaeologists used a new laser technology to remove layers of white carbon calcium deposited on the frescoes over the centuries without disturbing the paintings . They are located in the catacombs of St. Tecla , one of the 40 Roman catacombs under Rome . It sits under a modern eight-story building in a working-class neighborhood . It is closed to the public and its entrance is mostly hidden . The Vatican spent about 60,000 euros ( about $ 74,000 ) on the archaeological work , it said . The apostles were a group of a dozen men , according to Christian tradition , who spread the gospel of Jesus after his crucifixion . CNN 's Hada Messia contributed to this report .
Images found in painting on ceiling of what is thought to be tomb of noblewoman . Oldest known painting of Apostle Paul previously found in same location . Two years of work were needed to reveal the images .