Published: Nov 28, 2012 1:42 PM EST

CLEARWATER, Fla. (AP) - A medical examiner has determined two boys killed in a murder-suicide involving their mother drowned.
    
The Tampa Bay Times (http://bit.ly/UYoYfi ) reports the deaths of 9-year-old Zander Brown and his 5-year-old brother Zayden have been ruled homicides. Their 34-year-old mother Dawn Brown committed suicide by hanging herself from a ceiling fan in their Clearwater home.
    
The Times reports the medical examiner found unusually high levels of diphenhydramine, a chemical compound found in sleep medications, in the boys' blood. The drug was ruled a contributing condition in their deaths.
    
Pinellas County Sheriff's spokeswoman Cecilia Barreda says without more evidence investigators can't be sure that the mother used medication to render the children unconscious before drowning them.
    
The boys' father Murphy Brown found them dead in bed when he returned home Sept. 22.
    
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Information from: Tampa Bay Times (St. Petersburg, Fla.), http://www.tampabay.com.

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