The investigation into tragic actor Corey Haim’s death is stepping up. Approximately 20 doctors have been handed subpoenas which will force them to give evidence in connection with the tragedy.

“The Lost Boys” star passed away in Los Angeles earlier this month, after collapsing at his mum Judy’s house.

The cause of death is still unknown, but California’s Attorney General Edmund G. Brown Jr. has fueled speculation Haim died from a drugs overdose by revealing the actor had obtained an illegal order for painkiller OxyContin.

Haim was linked to a drug ring and could have had up to 20 doctors unknowingly writing prescriptions for him.

Officials at the Los Angeles County Coroner’s Office have identified the medics and sent them subpoenas, according to TMZ.com.

The doctors are reportedly from Los Angeles, Orange County and Ventura County in California.

It’s unclear how helpful the medics will be to the investigation because seven of them have reportedly claimed they never met Haim or prescribed medications for him.

The leaders of the apparent San Diego drug ring stole prescription pads from the doctors and wrote out illegal medication orders for clients. One such client is believed to be Haim.