Nasdaq trading frozen for three hours by computer glitch

A computer error froze trading on the Nasdaq stock market for three hours on Thursday, raising concerns about electronic systems that now dominate exchanges.

The Nasdaq is the second largest stock market operator in the US and is host to the majority of the big name tech firms including Apple, Microsoft, Google and Facebook, along with over 3000 other companies from 37 countries.

The glitch meant Nasdaq announced a hault to trading shortly after midday causing buying and selling to be suspending during the period. Trading resumed at 3:25 p.m.

Nasdaq said on its website that errors in the feed which disseminate quotes and prices caused the problem. Since, the stock market's boss has blamed third party firms for the glitch. "We have to be aware that the other person will not always act in the proper way," he told CNBC.

A computer failure does not put investors at risk of losing money unless they happen to be trading stock at the exact moment when an error occurs, in which case they would have to cancel the transaction. .

"Clearly it's an annoyance, but it doesn't in any way affect the value of your underlying assets," Marty Leclerc, chief investment officer at Barrack Yard Advisors told AP. "Warren Buffet used to say that if you own a stock you ought to be comfortable with it even if the market were to close for a year."

The White House, Treasury Department and other US agencies have said they are monitoring the disruption.

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