WASHINGTON--Grand juries could hand down the first indictments from two investigations of fraud within the General Services Administration (GSA) in about eight weeks, Deputy Attorney General Benjamin Civiletti said yesterday.

But another Justice Department official said the cases "in a so-called advanced stage of development" involved "relatively low-level" persons.

A Baltimore grand jury is looking into alleged fraud at GSA self-service stores and in the use of government credit cards.

In Washington, a grand jury has been investigating alleged bribery and fraud in repair and alteration contracts for federal buildings in the Washington area.

An investigation of the GSA in Boston is not as far along as the ones in Baltimore and Washington, Civiletti said.

Getting Together

Civiletti told a Senate Governmental Affairs subcommittee yesterday the Carter administration has agreed to set up an interagency strike force to coordinate the various investigations of the GSA.

Assistant Attorney General Philip Heymann told the subcommittee there was no need to appoint a special prosecutor to handle the investigation.

Not Alone

Fraud and white-collar crimes against he government are not limited to the GSA. Elmer B. Staats, comptroller general of the GSA, said at the subcommittee hearing.

"No one knows the magnitude of fraud against the government," Staats said, estimating that illegal activities could cost taxpayers between $2.5 and $25 billion a year.