After reaching the highest point in its 13-year history in May, Maryland's index of economic indicators was down in June, signaling a possible slowdown of the economy by fall, experts say.

On June 30, the Maryland index was at 107.361, compared with 109.193 at the end of May, according to Data Resources Inc., which designed the index.

"The tendency is to view June's decline as an aberration, but there are other factors that suggest caution," Bradley Hunter, a research economist for Data Resources, said.

Hunter said he is not forecasting sharp declines in the state's economy, but "on balance, the fall will be somewhat weaker."

The index was set up in January 1974 and was assigned a value of 100. Its lowest point since then was 95.554, reached January 1983, during the last recession.

The index is based on several items, including the amount of consumer credit used, construction permits issued, number of hours firms in the work week and company inventories.

Hunter said he expected Maryland to continue in the middle of the group of South Atlantic states studied by Data Resources, a Lexington, Mass., firm. Maryland's economy, he said, will not be as strong as Florida, nor as weak as West Virginia.

"Maryland usually follows the national trend," Hunter said. "We expect that will continue. Maryland's performance will be stronger in some ways because it is less dependent on manufacturing than it once was."

He said most of the state's employment growth will come in the suburbs near Washington