Amazon, Apple, Alphabet stock prices go haywire

Traders were left gawping at their Bloomberg and Reuters terminals on Tuesday, after they showed shares in companies such as Amazon and Microsoft plummet more than 50 per cent and Apple shares rocket as much as 348 per cent higher, before freezing at $US123.47.

A routine test of the Nasdaq exchange system, ahead of the US Independence Day holiday, appears to have been performed at a different time on Tuesday and data sent to the likes of Bloomberg, Reuters and Google Finance was accidentally interpreted into real time prices.

Shares in Microsoft appeared to soar 79.1 per cent higher, while eBay rocketed up 253.5 per cent. Zynga, a mobile and social game maker, experienced a staggering 3,292 per cent leap, making it temporarily more valuable than Goldman Sachs.

Vendors insist they were not informed of the earlier test times, though all declined to officially comment, while Nasdaq is adamant the systems test occurs daily and no trades have been incorrectly confirmed.

The prices on Nasdaq's official website were unchanged however pricings on Bloomberg, Thomson Reuters and Google Finance showed a raft of sharp movements before all registering $US123.47 for a period of time.

In a statement, Nasdaq said the glitch was related to "the improper use of test data" sent out to third party data providers and that it was working to resolve the matter.

The data vendors Thompson Reuters, Google Finance and Bloomberg had all rectified the confusing data by the time the ASX closed on Tuesday afternoon.

Generally data vendors disregard the test data, though this it is not clear why this did not happened for the Nasdaq on Tuesday.

The inaccurate price movements gave Apple a theoretical market capitalisation of $US3.4 trillion, as opposed to its $US751 billion valuation at Friday's close. Bed Bath & Beyond, meanwhile, was indicating a $US17.9 billion market valuation instead of $US4.4 billion.

No party has been able to confirm why the likes of Apple, Alphabet and Amazon were altered but Facebook and some other listed stocks were unchanged.

The exchange's full statement said: "Nasdaq is investigating the improper use of test data distributed by the UTP [Unlisted trading privileges] and consumed by third parties. As part of its normal process, the UTP distributed test data and certain third parties improperly propagated the data. Nasdaq is working with third party vendors to resolve the matter."

The issue is reminiscent of the ASX outages, though less severe, that occurred in September last year.