The toxic chemical dioxin was found outside a fragrance plant in a residential neighborhood, less than a tenth of a mile from a grammar school, Gov. Thomas Kean said yesterday.

Although there was no evidence of contamination outside the Givaudan Corp. plant, Kean ordered part of the plant closed and the soil covered with tarpaulins to keep the dioxin in place.

Eleven sites in New Jersey are being tested for suspected dioxin contamination, and the Clifton plant is the third where the deadly substance has been found.

Results received Friday of preliminary tests at Givaudan last week showed up to 11 parts per billion of dioxin in soil and on the ground next to the plant's hexachlorophene manufacturing section, which was ordered shut down, Kean said.

The results were the highest dioxin readings found at an active plant in New Jersey, said Carl Golden, the governor's chief spokesman.

Higher levels were found at the former Diamond Alkali Co. herbicide plant in Newark, but that site is abandoned and not as close to homes as the Givaudan plant. About 100 homes are within a half-mile.

The public school, which has about 230 children, is located as close as 500 feet from plant property, police Sgt. Richard Less said.

The federal Environmental Protection Agency considers 1 part per billion of dioxin to be hazardous to health. Dioxin has been linked to cancers, birth defects and liver and kidney ailments.

Federal Environmental Protection Agency workers began taking samples from soil and from air-conditioning filters at homes and businesses near the plant, said Robert E. Hughey, commissioner of the state Department of Environmental Protection. Results are expected by Thursday, but Hughey said he was confident that no dioxin had been tracked off-site.