The head of the US Securities and Exchange Commission has warned bitcoin and other cryptocurrency investors to beware of scams and criminal activity in the sector. In the financial regulator's strongest statement yet, SEC chair Jay Clayton said: "If a promoter guarantees returns, if an opportunity sounds too good to be true, or if you are pressured to act quickly, please exercise extreme caution and be aware of the risk that your investment may be lost." The warning comes at a time when many people have begun to take out mortgages to buy bitcoin. From a report: Clayton's statement was also issued the same day the SEC took regulatory action to halt an initial coin offering (ICO). "Recognize that these markets span national borders and that significant trading may occur on systems and platforms outside the United States. Your invested funds may quickly travel overseas without your knowledge," he wrote, in a sentence that was in bold. Clayton's statement referenced some of the crucial debates that have swirled around the rise and regulation of crypto-assets like bitcoins. Are these currencies? Commodities? Or securities? The statement notes in a footnote that bitcoin in the US has been designated a commodity. But the broader answer seems to be that while it depends from case to case, initial coin offerings, at least, are more likely to be scrutinized and held to the same bar as securities offerings.