In February 2010, the Prague city authorities approved a request by Danish scientists to exhume the remains, and in November 2010 a group of Czech and Danish scientists from Aarhus University collected bone, hair and clothing samples for analysis. The scientists, led by Dr Jens Vellev, analyzed Tycho's beard hair once again. The team reported in November 2012 that not only was there not enough mercury present to substantiate murder, but that there were no lethal levels of any poisons present. The team's conclusion was that "it is impossible that Tycho Brahe could have been murdered". The findings were confirmed by scientists from the University of Rostock, who examined a sample of Tycho's beard hairs that had been taken in 1901. Although traces of mercury were found, these were present only in the outer scales. Therefore, mercury poisoning as the cause of death was ruled out, while the study suggests that the accumulation of mercury may have come from the "precipitation of mercury dust from the air during [Tycho's] long-term alchemistic activities". The hair samples contain 20–100 times the natural concentration of gold until 2 months before his death.