Preliminary investigations suggested that no foul play was involved, police said.
Companies like First Meta Exchange allow users to exchange between different national and virtual currencies such as bitcoin.
The credibility of virtual currencies, in particular bitcoin which is the highest-profile, has suffered in the last week from the closure of two exchanges. One of these, Mt Gox, lost almost all the virtual currency in its system and filed for court protection in Japan last Friday.
Radtke was appointed to lead the start-up in 2012, and the company received nearly half a million dollars in funding in the same year.
"The First Meta team is shocked and saddened by the tragic loss of our friend and CEO Autumn Radtke," the company said in a note on its website.
DPA