The shutdown was the worst in more than four years and eventually, the ASX told the market it would not re-open today but would continue to investigate the problem.

More than 2000 companies are listed on the ASX, which is itself, a listed company and must disclose anything that may impact earnings.

Corporate watchdog the Australian Securities and Investments Commission said the outage was of “significant concern”

“ASIC remains in regular communication with ASX, market participants, and members of the Australian Council of Financial Regulators. We are focussed on ensuring that ASX reopens in an orderly manner on Tuesday 17 November, and that market integrity is not compromised. ASIC will also monitor for any impacts resulting from the failure of ASX Trade to open for most of the day.

“It has had a significant impact on the market, including market participants and investors,” ASIC said.

“We are focussed on ensuring that ASX reopens in an orderly manner on Tuesday 17 November, and that market integrity is not compromised. ASIC will also monitor for any impacts resulting from the failure of ASX Trade to open for most of the day.

“The ASX is one of the world’s most active and visible public markets and forms a critical part of Australia’s national economic infrastructure.  Well-functioning financial market infrastructure is critical to the integrity and reputation of the Australian equity market and the trust and confidence investors have in it. As the primary equities market in Australia, ASX peforms a vital role.

“Market licensees are required to operate a market that, to the extent reasonably practicable, is fair, orderly and transparent, and to have sufficient resources (financial, technological and human) to operate the market, including for any outsourced services. “Following the reopening of the market, ASIC will determine whether ASX followed the relevant regulatory requirements under the Corporations Act and met its obligations under its Australian Market Licence.

“In addition to ASIC’s expectations that this outage will be resolved as soon as is possible in a safe manner, ASX will be required to provide a full incident report to ASIC.

“We note that the Chi-X market remained open for participants to trade ASX listed equities, as well as Chi-X quoted ETFs and TraCRs.”

There are about 1 million trades a day on the ASX which has a value of more than $2 trillion.

Hacking is not expected to be an issue, but there are reports that there was a software upgrade over the weekend.

The ASX was also embarrassed by the failure of its new website when it launched a month ago.

The only hint the ASX gave was that the shutdown related to a data problem.

“The ASX equity market is currently paused and there is no trading while we investigate market data issues,” a spokesman said.

“ASX apologies for the disruption and is working to rectify the issue as soon as possible.

“The underlying cause of the issue has been identified and a resolution path is in place to allow trading to commence tomorrow at 10am.”

The S&P/ASX200 benchmark index closed up 79.0 points, or 1.23 per cent, to 6484.3 on Monday.

The All Ordinaries gained 77.6 points, or 1.17 per cent, to 6687.0.