A Canadian biologist say his trek in southwestern China has shattered a myth of \"killer mushrooms\" being responsible for 400 unexplained deaths in the region. Jianping Xu of McMaster University in Ontario said his investigations were triggered by a 2010 article in the journal Science, claiming Trogia venenata mushrooms contained high concentrations of the metal barium and linking them with high blood pressure, cardiac arrests and sudden deaths in southwestern China over the past 30 years. \"Although there was no published evidence supporting the theory that barium in the T. venenata mushroom was the leading culprit of what was called Sudden Unexplained Death, it was picked up as a fact by almost all of the major news media,\" biology Professor Xu said. \"These reports caused significant concern among the public about potentially high levels of barium in wild edible mushrooms in southwest China.\" Every summer for the last four years Xu and colleagues have trekked across the Yunnan province, collecting T. venenata and other mushrooms from villages severely impacted by these deaths. Analysis of the mushrooms found barium concentrations so low a 150-pound person would have to ingest at least 75 pounds of dried T. venenata to create a lethal amount, the researchers said. While barium can\'t be completely ruled out as a contributor to the deaths since high levels of the metal were found in the blood, urine and hair samples of some victims, Xu said, his study does suggest that barium in mushrooms was unlikely the leading cause. \"Though there are a couple of leads,\" he said, \"further investigation is needed to discover what the true cause was for these mysterious deaths.\"