Pope Benedict XVI has written to bishops worldwide to explain the church's much-criticized handling of the case of a Holocaust-denying bishop, whose excommunication was recently lifted by the pontiff. The explanation is contained in a letter in several languages that will be released by the Vatican's press office Thursday. In announcing the letter Wednesday in a brief statement, the Vatican gave no details about the handling of the case of British-born Bishop Richard Williamson, who in a TV interview in January denied that 6 million Jews were killed in the Holocaust. Rome daily Il Foglio said that the pope acknowledges in the letter that the Vatican made "mistakes" in the handling of the entire case. The pope's bid to explain the case comes only a few days after Benedict confirmed that he would visit Israel in May as part of a pilgrimage to the Holy Land. Williamson told Swedish TV that about 200,000 or 300,000 were murdered but that none was gassed. Benedict's lifting of the excommunication of Williamson sparked outrage among Jewish groups and in Israel as well as among Catholic bishops in Germany. Without citing sources, the Italian daily reported that the pope writes that the Vatican should have been aware of Williamson's Holocaust-denying statements being carried on the Internet. The pontiff also reportedly faults the Vatican for not explaining its actions on Williamson in a "sufficiently clear" way, according to Il Foglio, a small conservative-leaning daily. Last month, Williamson apologized for the "hurt" that his remarks caused, but didn't recant what he said. The Vatican has called that apology inadequate. Bowing to criticism by Jewish groups, historians and others, the Vatican demanded on February 4 that Williamson "absolutely and unequivocally distance himself" from his Holocaust denial. After the furor, Williamson was ordered to leave Argentina, where he had been living, and returned to his native Britain. State prosecutors in Germany have opened a probe into whether Williamson broke German laws against Holocaust denial.