The federal government, through three separate agencies, is conducting more than a dozen investigations of the oil industry.

In addition to the investigation by the Energy Department's Office of Special Counsel, the cover a wide area of alleged wrongdoing, ranging from international conspiracy to fix prices to monopolistic practices in the United States.

The following is a summary of some of the investigations.

DOE's Office of Competition is supervising three investigations relating to independent oil firms. One seeks to determine whether major oil companies subsidize their own gasoline stations in an effort to force independents out of business. Another is looking at whether major oil companies have kept their pipelines small in order to deny independents access to them. The third is an effort to determine if independents get fair access to crude oil.

DOE has several investigations relating to developments this year. One is aimed at finding out why refiners' stockpiles were larger at the end of May than in January, even though supplies of gasoline were scarcer. Another is looking at why there was less gasoline and middle distillate oil (used in part for home heating) refined per barrel this spring than in earlier periods. A third examination is focused on the spot marker for gasoline.

The Justice Department's newest investigation is looking at whether this spring's gasoline shortages involved antitrust violations by the major companies. Other investigations are examining whether U.S. companies are controlling prices or supplies in the Persian Gulf in an anticompetitive way.

Finally, the Federal Trade Commission has had an antitrust case against eight oil companies for the past six years.