A bipartisan group of 43 senators yesterday asked Commerce Secretary Malcolm Baldrige to investigate possible national security problems associated with increased imports of gasoline and some other petroleum products.

The letter to Baldrige said that 111 American refiners have gone out of business in the past four years and that the operable capacity of U.S. refineries has dropped from 16.9 million barrels a day in 1983 to 15.6 million barrels.

"At the same time, the domestic demand for petroleum products rose to about 15.9 million barrels in 1984," the senators said.

"Domestic petroleum product demand continues to be satisfied only through a significant level of imports, which is shifting toward lighter refined products such as gasoline," the senators said.

"Further, over 1 million barrels of additional foreign refining capacity, most of which is in the Mideast, is expected to come on line within the next two years."

"Our vulnerability to crude-oil imports would be compounded by increased reliance on foreign refining capacity, which is particularly susceptible to terrorist attacks," the senators said.

A Commerce Department spokesman said the letter is being reviewed and, until then, the department will have no comment.

The request for the investigation was initiated by Sen. J. Bennett Johnston (D-La.) and was signed by other members, including Senate Budget Committee Chairman Pete Domenici (R-N.M.) and Sens. Robert Byrd (D-W.Va.), Lloyd Bentsen (D-Tex.) and Nancy Kassebaum (R-Kan.).

Four years ago, a group of senators asked Baldrige to investigate the potential adverse effects on national security of increased petroleum-product imports under section 232 of the Trade Expansion Act.

However, the government had conducted investigations in 1979 and 1975, and Baldrige said that the president has sufficient power to reduce petroleum imports without another investigation, the senators said.

U.S. petroleum refiners said yesterday that the loss of American refiners and the drop in operating capacity of refineries has resulted from low U.S. tariffs on imports, which cause foreign firms to divert those goods to the United States.

In addition, some countries subsidize their petroleum industries, and some U.S. refiners are suffering from the short-term costs of eliminating lead from gasoline, the refiners said.