It may have been the smell, or the fact that something seemed odd about an 8,000-gallon tank truck disposing of its contents down a Newark, N.J., sewer in the dead of night. But what cinched the case was when the arresting officer's shoes began to rot.

The bizarre incident was just one of several cited in court this week in Newark by New Jersey authorities as they described their investigation into the booming business of illegal disposal of chamical waste.

So serious has the problem become in New Jersey and other heavily industrialized states where tough new environmental rules have recently gone into effect that police say some frantic chemical companies have turned to organized crime for help in solving their disposal problems.

New Jersey law enforcement officials, working on a two-year grant from the Justice Department's Law Enforcement Assistance Administration, claim they have uncovered evidence that some chemical firms with disposal difficulties have obtained help from garbage trucking and disposal site operators with ties to organized crime.

New Jersey shut down its last legal land disposal site to chemical dumping nearly two years ago. The site handled chemical waste from as far away as Maine and Georgia. Since then the cost of disposing of such waste - much of which is toxic, cancer-causing or radioactive - has soared.

The land disposal cost the chemical companies or their carters between 5 and 10 cents per gallon of waste. Disposal sites that incinerate or specially treat chemical waste are still available in the state, but their specialized services can run as high as a dollar or more per gallon.

The result, said New Jersey Deputy Attorney General Robert T. Winter, has been a series of indiscriminate dumpings of highly dangerous chemical waste throughout the state and in other states as well.

New Jersey officials have indicted eight individuals and three business firms for illegal chemical dumping since last March.

In one instance state investigators poking around an unauthorized dump in the Newark meadowlands across the Hudson River from New York City uncovered a huge ditch into which an entire tank truck and its chemical contents had been shoved and loosely covered over.

Chemical wastes have been illegally dumped on dirt and the dirt used as landfill or on garbage which was later passed off as "clean" by disposal site operators, Winter said. One team of disposers working at night went into a residential street and dug up a vacant lot, filling the hole with 55-gallon drums of chemicals and disappearing before dawn, he said.

In the Newark incident, which took place last year, Winter said a cruising police patrol car came upon a large chemical tanker dispensing its load into a sewer. Four persons and a trucking firm were charged with the illegal disposal of chemical waste. In their trial, which opened in Newark this week, police produced the shoes of the arresting patrolman that had started to disintegrate when some of the tanker's contents slopped over them.

"A lot of these companies are caught in a real problem," Winter said. "There just is nowhere left for them to go. When some carter offers a no-questions-asked deal they take it."

New Jersey, with its heavy concentration of chemical processing firms, appears to be the center of the problem, officials said. But other states have had similar disposal incidents involving dangerous chemicals.

Rhode Island officials, alerted to unusually dense smoke coming from a private dump site in the southern part of the state last November, showed up one Saturday to investigate and cite the operator for pollution. While they were at the site six large chemical waste-laden tank trucks roared into the dump - all bearing New Jersey license plates.

Allen Rubine, an assistant state attorney general in Rhode Island, said his office has been investigating the illegal dumping of chemical waste in the state for links to organized crime.

In New York, federal officials said while they have not uncovered any criminal involvement they have had several serious problems with chemical dumping. In one a group of attorneys purchased a landfill near the city of Oswego in the northwest part of the state and allowed 7,000 drums of unlabeled chemicals to be buried. The Environmental Protection Agency, which is supervising the removal of the rotting drums, estimates the cleanup cost at well over $1 million.

Even more of a problem, according to officials, is the cost in potential groundwater contamination by buried chemical wastes. One southern New Jersey township lost its entire water supply several years ago when a cache of containers of chemical waste rotted and the contents seeped into the water table.

Moreover, federal environmental officials said the problem of illegal disposal appears to be growing. The last legal New Jersey disposal site was handling about 1 million gallons of chemical waste per week when it was closed."We checked the major legal disposal sites along the East Coast and none of them has expanded to handle that stuff," said a federal official in New York. "We don't know where it went but we do know it hasn't disappeared into thin air."