Lamar Odom overdosed on drugs, E! News has learned.

A source inside Sunrise Hospital in Las Vegas tells us that "drugs were found in his system," and doctors are treating the situation as an "overdose." Lamar remains unconscious and on a ventilator but is still alive. It also appears that the former Los Angeles Lakers player suffered from a "loss of oxygen but also possible stroke."

"So, likely there's brain damage, but they're not sure how much," the source adds. "Virtually every drug imaginable was found in his system."

Lamar appears to have suffered an "ischemic stroke," which is caused by a blood clot preventing blood flow to the brain. This type of stroke is often associated with a cocaine overdose, among other drugs. Our source adds that Lamar "had been partying since Friday."

"He was doing crack cocaine all weekend and he choked on his mucous," the insider explains. "They're now having to fix all the damage it has done."