TORONTO (Reuters) - For about an hour and 11 minutes last Friday afternoon, traders in Canada’s biggest stock exchanges were left in the dark, as the stock market operator battled with a hardware failure.

A darkened television studio is seen at the offices of TMX Group, which operates the Toronto Stock Exchange, after the company announced it was shutting down all markets for the rest of the day after experiencing issues with trading on all its exchange platforms in Toronto, Ontario, Canada April 27, 2018. REUTERS/Chris Helgren

Those 71 minutes are an eternity for traders, some of whom had no access to critical data, market participants said. At the time, Toronto Stock Exchange operator TMX Group Ltd (X.TO) said only that it was experiencing trading issues on all its exchange platforms, and it eventually said it would shut down trading earlier than usual that day.

TMX, which later blamed the market outage on a hardware failure, rectified the issue and trading resumed on Monday.

Now, market experts are questioning whether TMX communicated swiftly enough on Friday about the shutdown that occurred more than two hours before the usual close of trading. The episode has also exposed retail investors’ heavy reliance on TMX for market data, which weighed on their ability to execute trades.

“If there was a smaller time window between TMX saying they have a problem and confirming they were not going to open, that would have been better,” Chris Sparrow, director of trading analytics at LiquidMetrix and a former member of the Market Structure Advisory Committee at the Ontario Securities Commission (OSC), said on Tuesday.

“There are a lot of calls to action,” he added. “I would be surprised if the regulators are not currently investigating this.”

The Ontario Securities

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