TOKYO, June 24 (Reuters) - Oil prices fell after voting ended in a UK referendum on whether to stay in the European Union, with early returns indicating a close result and prompting big swings in the value of sterling.
U.S. crude CLc1 was down 35 cents at $49.76 a barrel at 0001 GMT.
Brent crude LCOc1 was down 27 cents at $50.64 a barrel.
On Thursday, both contracts rose sharply, rallying on optimism the Britons would vote to stay in Europe.
The first few official results on Friday put the 'Brexit' campaign ahead, although opinion polls suggest that the vote will end a victory for the 'remain' campaign.
With results in from the first five of 382 voting districts, those in favour of ending Britain's 43-year membership had a small lead, but it was too early to discern a reliable trend.
Sterling slumped to $1.4475 GBP= , having earlier hit a high for the year at $1.5022. The euro turned tail to hit $1.1324 EUR= and the yen recouped early losses to stand at 104.96 per dollar.