NEW YORK • The prices of several big-name Nasdaq-listed stocks appeared on some websites to either spike or plummet well after the closing bell on Monday, seemingly due to a glitch related to the market data that runs the largely automated markets.

At around 6.30pm local time, the prices of Amazon and Microsoft stocks appeared to have lost more than half their value, while Apple shares appeared to more than double. Google parent Alphabet and eBay shares were among others that all appeared to be priced at US$123.47 on some financial news websites on Monday.

The actual prices of the stocks were not affected and no trades were completed at that price, a Nasdaq spokesman confirmed.

Nasdaq said in a statement it was investigating the improper use of test data distributed by third parties. Prices on Nasdaq's website were not affected.

"I've seen quite a few fat finger incidents when you get a funny price briefly," said Mr Eric Moffett, a portfolio manager for the T. Rowe Price Asia Opportunities Equity Fund in Hong Kong.

"When I saw the series of alerts, I figured something was up," he told The Wall Street Journal.

Nasdaq and other United States stock exchanges closed early on Monday ahead of the Independence Day holiday yesterday.

A slew of high-profile trading glitches have roiled markets in recent years, the Wall Street Journal said.

In May 2010, the Dow Jones Industrial Average plunged nearly 1,000 points in a matter of minutes before rebounding quickly in what widely became known as the "flash crash." In August 2013, a technical glitch knocked out trading in all Nasdaq Stock Market securities for three hours due to a problem with the data feed that supplied trade information. In July 2015, a glitch forced the New York Stock Exchange to halt trading for nearly four hours.

Testing of stock exchange software is mandated by the US Securities and Exchange Commission, and happens on a regular basis to help prevent electronic glitches, often using test symbols and historical data, Reuters reported.