Thirteen toxic chemicals, including those which, when surreptitiously dumped into Louisville's main sewage treatment plant two years ago forced its closing, have been found in 600 steel drums, some leaking, in a field flooded by the nigh waters of the Ohio River.

Federal and state officials say there has been no serious contamination of the Ohio, and that the chemicals pose no threat to downstream cities that draw their drinking water from the river.

The U.S. Environmental Protection Agency tested the contents of 27 of the drums in April 1977. They found two suspected cancer-causing agents, xylene and toluene, and 11 other chemicals considered toxic. Among them are hexachlorocyclopentadience and octachlorocyclopentene, the chlorinated hydrocarbons discovered in Louisville's sewer system in March 1977. The agency decided to leave the barrels there because at the time they thought it was a stable site.

After that discovery, Louisville's main sewage treatment plant was shut down for three months, during which 100 million gallons of raw sewage was dumped into the Ohio every day. Two of the city's sewer lines are still closed for cleanup operations, causing as much as 15 million gallons of untreated sewage to be pumped into the river each day.

Last month, in what environmentalists considered a landmark case, a federal court convicted Donald E. Distler, president of Kentucky Liquid Recycling Inc. of New Albany, Ind., on two counts of discharging pollutants into a federal waterway in connection with the dumping.

The charges are criminal misdemeanors, and it was the first time a criminal conviction had been obtained in such a case. Distler was acquitted on two charges of conspiracy, and a codefendant was acquitted.

Sentencing for Distler is set for Feb. 5. He could be sentenced to one year in jail and fined up to $25,000 on each count.

The 600 barrels that now threaten the Ohio are on property 15 miles southwest of Louisville near West Point, Ky., owned by Distler's parents. Mr. and Mrs. William Distler. Donald Distler has denied having anything to do with the drums, and his parents have refused to comment.

Officials became concerned when recent heavy rains caused the Ohio to swell from its banks, scattering the drums and rupturing some. Many have been found floating in Stump Gap Creek, which flows into Pond Creek, which flows into Salt River, which empties into the Ohio.

The drums are scattered over an area of at least half a square mile. EPA spokesman Ben Eason said the cleanup could take two weeks.

At the request of Kentucky Gov. Julian Carroll, the EPA last week allocated $100,000 for the emergency cleanup of the drums, many of which are rusted and dented, and some of which are leaking. OH Materials Inc. of Findley, Ohio, has been hired to recover the barrels and move them to higher ground, where their contents are to be pured into federally approved containers.

It will then be Kentucky's responsibility to transport the chemicals for disposal. Officials say they will be taken to an approved landfill site, probably one in Livingston, Ala.

While officials say the chemicals pose no immediate hazard to the river, the EPA this week will be sampling water in the area to ensure that drinking supplies have not been fouled.

State and federal officials are also trying to decide what to do about a second site several miles away, known as "the valley of the barrels." They said thousands of drums are heaped at the unauthorized site, but the barrels' contents are not known.

The EPA has identified 638 chemical dumping sites in the United States that "pose imminent hazards to public health."