The Diocese of Mainz said it had preliminary indications that two people abused pupils boarding at the Bensheim Konvikt in the 1970s. State prosecutors have been informed, a statement said.
The director of the dormitory, where children attending a nearby secondary school boarded, was also implicated in sexual abuse allegations, it said. He "left the service of the diocese" in 1979 before the convent closed for "economic and educational" reasons.
The scandal erupted in January when an elite Jesuit school in Berlin admitted systematic sexual abuse of pupils by two priests in the 1970s and 1980s, and has now engulfed 19 of Germany's 27 dioceses.
Also implicated is a boarding school attached to the Domspatzen ("Cathedral Sparrows"), Regensburg cathedral's 1,000-year-old choir. The choir was run for
29 years by Georg Ratzinger, brother of Pope Benedict XVI.
Most of the priests concerned are not expected to face criminal charges because the alleged crimes took place too long ago, but there have been growing calls for a change in the law and for the Church to pay compensation.
The German scandal is one of several to have rocked the Catholic Church in recent years, notably in Ireland where one priest admitted sexually abusing more than 100 children, and this week in Austria and the Netherlands.
Federico Lombardi, a spokesman for the Vatican, said Tuesday that German, Austrian and Dutch Church leaders had acted "rapidly and decisively," stressing that sexual abuse went far beyond church walls.
The chairman of the German Bishops Conference, Robert Zollitsch, was to meet the pope on Friday at the Vatican to discuss the cases.