After Ellen Krips' cousin died of an overdose of extremely potent drugs last week, the heroin addict's first thought was not how she could avoid the bad junk.

It was more like: I have to get some of that stuff.

A bad batch of drugs for sale on the streets of Philadelphia and southern New Jersey has killed at least nine heroin users over the past two weeks. And while authorities are warning people to stay away from the stuff, they are afraid some junkies are drawing the wrong lesson.

Like Krips, 32, they are intrigued by the possibility of a powerful new high.

Investigators are trying to determine exactly what is in the stuff, which is being sold as heroin under such names as "Flatline" and "Capone." Since Friday, about 70 people have been hospitalized.

Tests done in one community show that what was sold as heroin was mostly fentanyl, a drug 80 times more powerful than morphine. It is used to treat chronic pain and as anesthesia for open-heart surgery. No heroin was in the batch.

Medical experts say fentanyl, which has been harming Chicago-area addicts for a few months and has shown up mixed with heroin in Cleveland and elsewhere this year, can cause breathing problems and make users feel as if they are suffocating.

William Gamble, 40, said he was sickened last week. Hours after a state trooper warned him that "Flatline" was dangerous, Gamble bought three, $10 doses of "Capone." He, his wife and another man shot up in an abandoned house. The men passed out quickly, but both survived and were not hospitalized. His wife was not affected.

Warnings from police, counselors and news outlets have had the opposite effect on some addicts.

"If I tell someone I OD'd, they're coming to find that bag," said Gamble, who goes through seven or eight bags of heroin a day.

Authorities arrested 11 heroin users in Camden last week in an effort to track the drugs back to the dealers and their suppliers. By Tuesday, those dealers had not been found.

Some public health officials estimate that 10,000 people in the Philadelphia area are addicted to heroin. With major airports and seaports nearby, Philadelphia, New Jersey and New York dealers are known to sell heroin in highly pure forms.

Johnny "J.B." Brown, a drug counselor who cruises the streets of this impoverished city in an RV, offering HIV tests and other services for drug users and prostitutes, has been trying to warn users.

"You being careful out there? You know, there's some bad dope," Brown said Monday as a steady stream of drug users approached for snacks, condoms and bleach kits to clean their needles.

All of them said they have heard about the killer drugs. But they said stuff so strong that it kills is impossible to resist. And even if they wanted to avoid the bad stuff, they might not be able to, since it is never clear which bag might contain fentanyl or some other deadly substance.

"It's like Russian roulette," said addict Michelle Galante, 28, of Swedesboro, "just like any drug."

Stephen Marcus, medical director of the New Jersey Poison Control Center, said he hopes more publicity about the dangerous drugs will help uncover similar problems elsewhere. But he also knows that every news report might serve as a commercial for drug dealers.

"Will this make the drug abusers go out particularly looking for the stronger stuff?" he asked. "If it does, it's a double-edged sword."