LONDON — The British pound plunged suddenly in the early hours of trading in Asia on Friday before just as quickly making back most of its losses, puzzling currency trading experts but underscoring investor skittishness over Britain’s prospects as it moves to break away from the European Union.

The pound remained about 1.2 percent weaker compared with the dollar by the evening in London. While a fall of that degree is notable for a major currency, it paled in comparison to the pound’s unexpected drop of more than 6 percent over a span of minutes in the thinly traded currency markets early in the Asian trading day.

A sudden drop like the one on Friday is often called a flash crash, and it is sometimes caused by automated trades or a simple misplaced keystroke — a fat-finger error, as it is known on trading floors. In the case of the drop in Asia for the pound, also known as sterling, experts said they were hard-pressed to identify a single cause.

The Bank of England said later on Friday that Mark J. Carney, the central bank’s governor, had asked the Bank for International Settlements’ Markets Committee to look into “the events surrounding the flash crash in sterling during Asian trade.”