Houston's death spurs look at her doctors, meds LOS ANGELES (AP) - It's become standard-operating procedure when a celebrity dies too young - investigators immediately go looking through their nightstand and medicine cabinet. That effort is well under way in the death of Whitney Houston, with investigators saying Wednesday they have subpoenaed records from the singer's doctors and pharmacies who dispensed medication found in her hotel room. The inquiries are routine in virtually all death investigations, Assistant Chief Coroner Ed Winter said, noting that similar measures are taken when a person dies in a car crash, shoots themselves or, as in Houston's case, dies unexpectedly. It will be weeks before toxicology results reveal the medications and quantities, if any, that were in Houston's system when she died. The Grammy winner's history of substance abuse has added to the speculation that her death may have been caused by prescription drugs. Abuse of prescribed medications has skyrocketed in recent years. In 2008, more than 36,000 people died from drug overdoses - triple the number from 1990 - with most of these deaths caused by prescription drugs. Drug deaths, fueled by prescription drug overdoses, now surpass motor vehicle deaths, according to the Centers for Disease Control and Prevention. Investigators have not said what medications they have recovered from Houston's room at the Beverly Hilton Hotel. The singer was found underwater in a bathtub by a member of her staff hours before she planned to attend a chic pre-Grammy gala. Police have said there were no signs of foul play and Winter said there were no signs of trauma on her body when an autopsy was conducted on Sunday. Among the scenarios that will likely be explored is whether Houston was drinking before her death, which could compound the effects of any medications she was taking. "Sometimes people fall into a stupor when they're on a combination of drugs so they're difficult to arouse," said clinical psychiatrist and addiction specialist Dr. Karen Miotto at the University of California, Los Angeles. Sober people who fall asleep in the bathtub will wake up when water hits their face. An impaired person may not respond the same way. Even a small amount of prescription drugs combined with alcohol "can result in a state of unconsciousness and inability to rescue oneself from drowning in the bathtub," said Bruce Goldberger, a forensic toxicologist at the University of Florida. In celebrity-rich California, the sudden death of a star always sparks interest in their medical history. When actress Brittany Murphy and actor Corey Haim died, their prescription medications became an early focus. In April 2010, Jerry Brown, then California Attorney General, proclaimed Haim was the poster-child of prescription drug abuse and doctor-shopping. The former child star of films such as "The Lost Boys" and "License to Drive" had long struggled with addiction, but coroner's officials ultimately determined prescription medications played no role in his death, which was attributed to pneumonia and an enlarged heart. A similar finding was made in the death of "Clueless" star Murphy, whose December 2009 death was attributed to pneumonia, along with severe anemia and prescription drug intoxication. A coroner's report stated that Murphy, who had been sick in the days before her December 2009 death, showed no signs she abused medication. California maintains a prescription drug monitoring database known as CURES, which contains more than 100 million prescriptions and receives anywhere from four to six million additions every month. Law enforcement officers can review the data culled from pharmacies to check whether doctors are prescribing outside the course of normal medical practice and see if a patient is getting multiple prescriptions from various physicians, commonly known as doctor shopping. Brown, now California governor, touted the CURES program as attorney general and, in addition to Haim, launched high-profile investigations into the deaths of Michael Jackson and Anna Nicole Smith. Jackson's personal physician was convicted of causing the singer's June 2009 death by giving him a powerful anesthetic as a sleep aid, although investigators determined there was no criminal wrongdoing by seven other doctors who treated the singer. But as she struggled with drugs, her majestic voice became raspy, and she couldn't hit the high notes anymore. Only after the weeks-long investigation into her death is complete and a full autopsy report is released will the impact of drugs on the singer's body become known. Officials have cautioned against speculating too much about what killed the singer and downplayed the role prescription meds may have played in her case. "There weren't a lot of prescription bottles," Winter, the coroner's official, said earlier this week. Associated Press Writers Alicia Chang and Greg Risling contributed to this report. Anthony McCartney can be reached at http://twitter.com/mccartneyAP. Follow Chang's coverage at http://www.twitter.com/SciWriAlicia