What appeared to be an open-and-shut overdose on June 25 has mushroomed into an investigation that is getting more convoluted and suspicious by the day.

The L.A. County Coroner and LAPD are not buying the story of Dr. Conrad Murray, who says he gave Michael Jackson a relatively low dose of Propofol.

Sources cited by TMZ say that the L.A. County Coroner has determined Michael Jackson died from a lethal level of Propofol. There were "traces" of other drugs in Jackson's system, but nothing that would have killed him.

According to the search warrant affidavit, Dr. Murray said he gave Jackson 25 milligrams of Propofol shortly before the singer stopped breathing June 25.

Dr. Murray also said he had been giving Jackson 50 milligrams for the prior six weeks, but he felt the star might be forming an addiction so he cut back.

In reality, sources say it takes about 400 milligrams of Propofol for someone Jackson's size to sleep eight hours - 16 times what Dr. Murray says he gave.

Law enforcement sources simply do not buy that 25 milligrams would have in any way compromised Jackson, especially since he had a high tolerance.

Moreover, the L.A. County Coroner still can't pinpoint the time of Jackson's death - another sketchy part of Murray's story - but paramedics say when they arrived they believed he was dead for at least an hour and maybe longer.

According to Dr. Conrad Murray (and his phone records), this was the timeline:

• Murray administered Propofol to Jackson at 10:40 a.m.
• Then minutes later (10:50), he walked out, went to the bathroom and returned two minutes later (10:52) to find Jackson was not breathing. 
• Numerous phone calls totaling 47 minutes are made.
• He did not have anyone call 911 until 12:21 p.m. ... approximately an hour-and-a-half (or 82 minutes later according to some accounts).

Sources say that when Dr. Murray was interviewed by police two days after Jackson died, with his lawyer by his side, the doctor's account seemed "scripted."

So when did Michael Jackson really die?

Rigor mortis typically doesn't set in for at least three hours, if not longer. If it has not set in, the only way to approximate time of death is body temperature.

If a person dies, their temperature eventually rises or falls to the environment. For example, if he were in a 70 degree room, his body would fall to 70.

Body temperature typically drops a degree to a degree and a half per hour, but the problem is that when paramedics arrived the room was sweltering.

Jackson's body temperature could therefore still register in the 90 degree range, even if he were dead for a long time. Also problematic? Paramedics did not get a read on his body temperature as they were busy performing CPR on Jackson.

Bottom line ... no one knows.