United Kingdom government agencies are trying to determine if a cyberattack actually caused a trading outage in August 2019, The Wall Street Journal reported Jan. 5, citing people familiar with the matter.

In the past two months, a British intelligence agency has reached out to the London Stock Exchange Group PLC seeking more details about the outage, and the U.K.'s Treasury is also involved, the sources said.

On Aug. 16, 2019, trading on the FTSE commenced 100 minutes late, making it the worst outage in more than eight years.

An LSE spokesperson said the LSE "thoroughly investigated the root cause of the issue" and determined it was not a result of a cyberattack, but rather a "technical software configuration issue following an upgrade of functionality."

More details about the probe, including whether regulators or the LSE plan to take any further action, remain unknown, according to the report.