03/22/2012 AT 05:10 PM EDT
's official cause of death was due to accidental drowning, the Los Angeles County coroner's office confirmed Thursday.
The singer, 48, was also found to have cocaine in her system. Contributing factors of her death included heart disease and cocaine use, an investigation found. The report also found that Houston had marijuana, Xanax, Benadryl and other medication in her system.
"There was water found in her lungs that indicated to us that she was alive when she was submerged underwater," coroner chief Craig Harvey tells PEOPLE. "According to our tests, the level of cocaine was not necessarily a lethal level of cocaine. But her death was complicated by chronic cocaine use and heart disease."
Coroner assistant chief Ed Winter says the circumstances of Houston's death come down to two likely scenarios.
"She could've passed out first due to the intoxication from the cocaine, or she could've had a heart attack and then drowned," Winter tells PEOPLE. "It's probably one of those two scenarios."
Houston was found unresponsive and underwater in a bathtub at the Beverly Hilton Hotel on Feb. 11, a day before the Grammy Awards
, and was pronounced dead
at the scene soon afterward.
Coroner officials previously confirmed that prescription pill bottles were found in her room, but the number of pills were "not in alarming amounts."
Houston, who had long battled drug addiction
, was laid to rest
on Feb. 19 at the Fairview Cemetery
in Westfield, N.J., alongside her father, following a star-studded memorial the day before.