Bookmakers' odds on the chances of the United Kingdom leaving the European Union swung late Thursday evening — with some predicting that a so-called Brexit would indeed occur.
Reuters reported at about 4 a.m. in London (11 p.m. ET) that the frequently-cited Betfair had made leave the favorite, with 89 percent odds. The AFP, meanwhile, reported earlier that odds had changed "dramatically," and pointed to an exit.
For much of the period leading up to Thursday's referendum, gambling markets had pointed solidly in favor of the U.K. staying in the EU.
In fact, the betting odds of a remain win had risen from 58 percent earlier Thursday to 88 percent before polls closed at 10 p.m. in London (5 p.m. ET), according to Dow Jones.
Follow CNBC's live coverage of the voting results here.
— Reuters contributed to this report.