East Germany released its most vocal dissident from 2 1/2 years of house arrest today, sources close to his family said in West Berlin.

A state attorney reportedly told the dissident, Prof. Robert Havemann, that the indefinite house arrest order, issued in November 1976, was now suspended and he could travel throughout East Germany. No reason was apparently given.

Human rights groups in West Berlin added, however, that an investigation of allegations that Havemann violated customs and currency laws will be continued.

Havemann, 69, is a prominent chemist whose scientific work was interrupted because of differences with various regimes. He joined the Communist Party of Germany in 1932 and is a former member of the East German Party's Central Committee. He got into trouble with Communist authorities in the 1960s by speaking out for personal freedoms.

Havemann was confined to his home after he had ideological works critical of the form of communism practiced in East Germany published in the West.

Last month, he complained in a letter published in the West German press that the conditions of his arrest had been tightened and that members of his family were unable to carry out such tasks as shopping.

The legal proceedings filed against Havemann for alleged currency violations concern his earnings on book sales in the West.