The Vatican is investigating allegations of doctrinal deviation in the work of Brazilian theologian Leonardo Boff, liberation" espoused throughout Latin American by many Catholics.

The inquiry is being conducted in Rome by the Congregation for the Doctrine of the Faith, the same church body that earlier this month questioned Dutch theologian Edward Schillebeeckx and censured Swiss theologian Hans Kung. The inquiry focuses on Boff's 1972 book, "Jesus Christ Liberator," regarded as one of the basic texts of the liberation theology.

The Latin American church first endorsed the theology of liberation at as bishop's conference in Medellin, Colombia, in 1968. Although church conservatives have attacked the doctrine for more than a decade, the bishops reaffirmed their support for it at a similar conference presided over by Pope John Paul II in Puebla, Mexico, in January 1979.

Interviewed at the monastery outside Rio de Janeiro, where he lives and writes, Boff, professor of systematic theology at the Franciscan seminary of Petropolis and editor of various church publications, says he is baffled by the proceedings against him, which began in 1975 and have been periodically renewed.

"There are theologians with positions much more radical than mine, and nothing has happened to them," said Boff, 41, a Franciscan. "I suspect that what has provoked their vigilance is that I am constantly writing and speaking to conferences, universities, radio and television on behalf of the church's option if favor of the poor and oppressed of the Third World."

Like Schillebeeckx and Kung, Boff is a member of the editorial board of the progressive magazine "Concilium." Church sources here fear that a generalized crackdown on church liberals may by under way.

"It would appear that all of our little group are in trouble, not just me," said Boff. It was Schillebeeckx who informed Boff that the charges against him had been revived. Kung has written Boff a letter of solidarity.

Leading Boff's defense have been two influential Brazilian cardinals, Aloisio Lorscheider of Fortaleza and Paulo Evaristo Arns of Sao Paulo. Arns, who taught Boff theology, says he has argued Boff's case in Rome and calls his former pupil "a humble, brilliant and enormously spiritual man whose capacity for poetic, philosophical and theological expression has been recognized by all."

Officially, the charges against Boff have been placed by an Italian monsignor. They question his view of the divinty of Christ. But church officials here believe that the move is a political one that has the backing of the leader of the conservative wing of the the leader of the conservative wing of the Latin American church, Bishop Alfonso Lopez Trujillo, of Bogota, secretary general of the Latin American Episcopal Council.

"This whole thing smells of Trujillo," says one church leader here. "He doesn't like Boff personally, and over the years he has made it clear that he and his friends at the Curia in Rome look upon the theology of liberation as a Marxist heresy."

Church leaders here fear that any apparent lessening of official support for the theology of liberation could lead to renewed violence against the church. In the last decade, more than 800 priests, nuns and lay workers in Latin America have been killed, jailed, tortured, kidnaped or deported as a result of efforts to put the liberation theology into practice.

Last week, a rightist terrorist group called the Communist Hunt Command expolded a bomb in a cathedral outside Rio de Janeiro. In a note left in the church, the group warned Bishop Adriano Hipolito, a renowned supporter of the liberation theology, that he would be killed if he did not "stop preaching communist doctrine."

Three years ago, Hipolito, bishop of the crime-ridden slum archdiocese of Nova Iguacu, was kidnaped by members of the same organization. After being stripped, beaten and painted red by his abductors, he was dumped naked on a side road, threatened with execution. His car was blown up by a bomb in downtown Rio de Janeiro.