The NZX 50 index fell 0.3 percent when trading on New Zealand's stock market resumed after a three-hour outage over connectivity issues.
The benchmark index dropped 14 points when markets reopened at 3pm in New Zealand, and within 20 minutes was at 4413.521, down 0.6 percent on the day.
The stock market operator will investigate the outage, and will report back to the Financial Markets Authority and market participants in due course, it said.
The NZX experienced connectivity issues on a number of its systems around midday, and decided to halt all trading while it undertook an urgent investigation into the problem.
Shares in NZX fell 2.2 percent to $1.31.
In April, the Wellington-based company kept trading open when problems with its data feed kept retail investors in the dark over market announcements and live pricing.
The NZX launched the NASDAQ OMX X-stream trading platform last November as it looks to branch out into new securities trading, including derivatives and commodities.
The stock exchange had a major IT glitch in 2010 when failures in multiple hardware services disrupted index feeds until midday, meaning index pricing, such as the benchmark NZX 50 Index, wasn't available in morning trading.