After almost four years of work and three convictions, the special panel investigating alleged scandal in Maryland's school construction program said it will seek no more indictments although other crimes may have been committed.

The convictions of three men, including Alford R. (Skip) Carey Jr., the former head of the billion-dollar construction program, came in connection with allegations of bribery and political pressure in the award of contracts to build portable classrooms.

The three convictions stemmed from the investigation led by the special panel set up in March 1975 to investigate the tangled web of allegations that had begun to surface.

In its final report, issued last night, the panel said that despite "facts and circumstances strongly suggestive of criminality," it could do no more.

While all information suggesting that other crimes may have been committed was pursued, the panel wrote, "we are not satisfied that we could in good conscience and consistent with our professional obligations have sought further indictments."

In part, the panel said, its investigation was impeded by the one-year statute of limitations that existed in Maryland on the crime of conspiracy until this year.

Another impediment, the panel said, was the limitation imposed by Maryland law kin granting of immunity to grand jury witnesses.

Carey, the former school construction chief, was indicted in 1976 on charges of demanding and receiving bribes from agents of Globe Industries, of Durham, N.C.

The company received more than $4 million to build portable classroom buildings for the state.

Despite Carey's subsequent conviction in that matter, questions remained about the selection in 1974 of a Maryland firm, Amalgamated Modular Structures, Inc. (AMS) for a contract award.

AMS had links to the politically powerful Tidewater Insurance Co., whose owners included W. Dale Hess and Harry W. Rodgers III. Hess and Rodgers were convicted along with Maryland Gov. Marvin Mandel in a political corruption trial last year.

In its report, the panel said that after the trials involving the award to the North Carolina company, the panel members said they attempted to resolve "the many lingering questions" concerning the later bid award.

In that competition, Carey publicly listed four firms, including AMS and Coastal Trailer Co., as having submitted bids.

Coastal Trailer never entered a bid, but Carey later said he had made a mistake, and produced a document that he said showed that a firm called Atlantic Coastal Trailer Co. had actually submitted the bid.

The panel said it was "convinced that the so-called 'Coastal Trailer' bid was unquestionably a sham and contained a forged signature."

"Unfortunately," the panel added, "we have not been able to as certain with certainty the identity of the forger."

Despite its disappointment in tht inability to resolve all questions about the 1974 bid, the panel said it accepted the fact that "in the absence of truthful cooperation from those directly involved, not all mysteries can be solved."

The members were attorneys Norman P. Ramsey, Harry C. McPherson Jr. and M. Wayne Munday.

After newspaper articles appeared in 1975 about the contract awards in the portable building program, state Attorney General Francis B. Burch asked Mandel for permission to investigate. On March 7, 1975, Mandel announced that the special three-member panel of citizens would be named to investigate the charges. That removed from Burch the direct responsibility for the investigation.

In its report, the panel called the concept under which it was established "unprecedented" in Maryland.