Two Senate committees have offered immunity from prosecution in return for testimony from a key figure in the Cental Intelligence Agency's vast mind-control experiments conducted from 1949 through 1972, informed sources said yesterday.

The Senate Intelligence Committee, which looked into the program in 1975 and 1976, announced yesterday that it was reopening its investigation on the basis of new documents jelating to the project released by the intelligence agency in the last month.

Sources said the intelligence committee and the Senate Human Resources Committee both offered immunity to Sidney Gottlieb, the former CIA official who authorized most of the mind-control financial expenditures, according to the recently released documents.

Gottlieb received a similar grant of immunity last year from the Intelligence Committee.During-secret testimony he acknowledged destroying CIA drug and mind-control records in 1973 and said he could recall few details of the program.

Knowledgeable sources also said yesterday neither one had ruled out also calling CIA Director Stansfield Turner. Last month the two committees held public hearings at which Turner testified that only sketchy records on the mind-control program were available. Since then the CIA has announced the discovery of 14 boxes of mind-control records, and additional information on the program has been found in the library of a California junior college.

"We want to make damn sure this time that congressional inquiries are completely and not just partially satisfied," said an Intellgience Committee spokesman.

Sen. Edward M. Kennedy (D-Mass.) has scheduled hearings for Sept. 20 into the CIA mind-control program for his Human Resources Subcommittee on Health and Scientific Research.