Thefts of crude oil and gasoline have grown so numerous in the United States that the FBI has begun to spike shipments with chemicals in an attempt to trace fuel when it is stolen.

"We are marking oil with a chemical you can't see and can't smell," Roger Aarons, chief of the chemistry section of the FBI laboratory in Washington said in an interview. "So that if this oil is stolen we can make an identification later on that a particular batch of oil was the oil that was stolen."

Oil and gasoline theft is one of the fastest-growing crimes in America. One reason is price. Fuel oil is now so expensive that criminals everywhere consider its theft a lucrative trade. Another reason is that stolen fuel is easy to dispose of, in part because it can't be identified as stolen and in part because there are so many people in the oil brokerage business. Houston alone has more than 100.

"Crude oil and gasoline have no unique characteristics, no matter who makes it," FBI Inspector Dana Caro, deputy assistant director of the bureau's organized crime division, explained. "It's very easy to get rid of the stuff."

The FBI now is investigating as many as 225 cases of stolen fuel, ranging from the hijacking of a 25,000-gallon tank truck to the theft of hundreds of thousands of gallons of crude oil right out of Wyoming's fields. There are dozens of theft cases in the nation's major ports and along the nation's major waterways, where thousands of gallons have been siphoned from barges when they make stops along the way.

"Oil fraud and theft is a major national problem," the FBI's Caro said. "It's the gold of the '80s."

The FBI began looking into what it calls "energy fraud" in 1978, assigning 10 agents in its Houston office. The bureau now has energy fraud details in its offices in Dallas, Denver, Pittsburgh, Oklahoma City and New Orleans. The FBI has also begun to assign undercover agents to major refineries in the southwest where there is evidence that organized crime may have infiltrated.

"A lot of the thefts we're looking at involve a sensitive knowledge of the oil industry," Caro said. "People on the inside appear to be involved in many of these thefts."

Some of the cases the FBI is looking into include thefts of crude oil right out of the pipelines that carry it from the fields where it's produced. The largest such thefts have been from the fields of Wyoming, especially the Wind River Indian Reservations.

"These thefts give us the biggest concern," Caro said. "They've involved the most oil and it's the easiest oil to steal."

Oil thefts also have occurred in every major U.S. port, notably in Houston and New Orleans, where tankers at anchor have been tapped. Gasoline has been siphoned out of storage tanks in New York, Philadelphia and Baltimore. Barges carrying jet fuel, gasoline and heating oil on the Mississippi River have been robbed.

The FBI has targeted the barge traffic on several major waterways in an attempt to find the oil theives. At the barge owners' request, the bureau is spiking the million gallons of fuel on a barge with a few gallons of a chemical it will not identify but which can be detected in its laboratory in a very simple test. If the oil is stolen, the bureau hopes to find enough of it on the market to test, identify and trace to the thieves.

"For a while, we weren't getting company requests to mark their oil even though they knew it was being stolen," the FBI's Roger Aarons said the other day. "Now that the price is so high and so much oil is disappearing, we're getting lots of requests. The companies are no longer tolerant of oil theft."