Police in Naperville and McHenry County were comparing notes Wednesday, working to determine whether the potent Ecstasy-like hallucinogen that apparently took the life of an 18-year-old Naperville woman over the weekend also killed a teen in the city of McHenry a week earlier.

In Naperville, Sara Aeschlimann died Sunday after apparently ingesting what she thought was Ecstasy, a stimulant popular in the Chicago-area club scene. What Aeschlimann actually took, police said, were several pills containing paramethoxyamphetamine, or PMA, a substance that experts said can be a very deadly compound.

The white pills Aeschlimann apparently took bore the three-diamond logo of the Mitsubishi company, a description that police in McHenry said matches the logo on the tablets taken by 17-year-old Steve Lorenz on May 7. Lt. Gary Wigman said the Lorenz case had been classified as a fatal Ecstasy overdose, but investigators will now shift their focus to include PMA.

Wigman said his department and the McHenry County coroner's office are awaiting the results of a crime lab analysis of the pills Lorenz ingested.

"The street name is Double-stack," Wigman said, which is the same street name of the pills in the Naperville case.

"We have linked up with police in McHenry," said Naperville Police Sgt. Ray McGury, supervisor of the department's major crimes unit. "At least preliminarily, it appears we are dealing with the same substance."

Police were continuing to try to identify a common source of the drugs. McGury said Naperville police have been in contact with law enforcement agencies across the area, and have determined that PMA is relatively new to the Chicago scene.

Drug experts said PMA often is passed off as Ecstasy, but is far more dangerous. A synthetic drug with no known medical uses, PMA surfaced in Australia in 1994 and has been linked to deaths in Canada, experts said.

Dr. Wilkie Wilson, a professor of pharmacology at Duke University Medical Center and a co-author of the 1998 book "Buzzed: The Straight Facts About the Most Used and Abused Drugs From Alcohol to Ecstasy," said a problem emerges when users who think they are taking Ecstasy sample PMA.

"A dose of Ecstasy that is `safe,' so to speak, can be highly toxic if it's really PMA," Wilson said. "PMA has Ecstasy-like properties--it's also a stimulant. Ecstasy will raise your body temperature and blood pressure, but PMA does that in spades.

"These kids are dealing with some very powerful pharmacology."

In an interview Wednesday, David Lorenz said his son, Steve, died about 8 a.m. on May 7. The 43-year-old father said his son's friends told him Steve had been taking Ecstasy the night before he died.

Lorenz said his son and a few of his friends would hold parties in an upstairs apartment in his McHenry home, and that it wasn't uncommon for them to play music and dance into the wee hours of the morning.

Lorenz said he was only a few feet away when his son was pronounced dead as he lay on the apartment's floor.

"The (paramedics) told me not to go into the room, but I went in anyway," said Lorenz, a single father who raised his son on a trucker's salary. "I told them, `He's my son.' I held his leg and tried to bring him back by talking to him, but I knew he was gone.

"That's when I heard them say that they had a `flatline.'"

In the days after his son's death, Lorenz held a candlelight vigil in memory of his son, which was attended by hundreds.

"I just want to get the word out," he said. "I knew there were going to be other kids dying from this stuff, and now a girl in Naperville has just died from it. It's not going to stop."

While investigators waited to determine whether the two teens lost their lives to the same substance, PMA, experts warned that Ecstasy carries plenty of its own dangers.

The active ingredient in Ecstasy, methylenedioxymethamphetamine, or MDMA, is a stimulant that should not be underestimated, police and experts warned.

Dr. George Ricaurte of the Johns Hopkins Medical Institutions in Baltimore, conducted a study for the National Institute on Drug Abuse that showed steady use of Ecstasy damages the brain.

Ricaurte's work used brain-imaging technology to show that use of MDMA can harm neurotransmitters, affecting things like mood and memory.

Like PMA, Ecstasy can quickly raise body temperature and boost the heart rate, Ricaurte said, leading to cardiac arrhythmia and even cerebral hemorrhaging.

"It can happen sporadically," Ricaurte said.

Police and representatives of the Drug Enforcement Administration in Chicago have also said that Ecstasy's manufacture can lead to problems. The mixture that makes up a typical pill changes from batch to batch, and can often include substances more potent than MDMA.

Investigators said Ecstasy use has been on the rise in recent months in the Naperville area, and in McHenry County as well.

Sgt. Todd Rohlwing of the North Central Narcotics Task Force, which covers DeKalb, Kane and McHenry Counties, said his unit has watched more and more teens experiment with the substance.

"Ecstasy is definitely on the rise," he said. "It's an up-and-coming drug."

The DEA has reported a growing problem nationally as well, recently releasing an Ecstasy bulletin. Special Agent Mike McManus said the DEA expects to hold an Ecstasy conference in Washington in August.

Only one person has been charged so far in connection with the Naperville death. Garrett Harth, 21, of the city, is being held on drug possession and distribution charges. Police said Harth, who was with Aeschlimann when she went into convulsions, purchased "Double-stack White Mitsubishi" believing it was Ecstasy.