(Bloomberg) -- It was just one trade of 5,000 shares, and it happened after the regular trading day. But it was enough to spike the price of the world’s largest mining company.

BHP Billiton Ltd.’s Sydney stocks jumped as much as 6.1 percent late Friday, their biggest move in two years, after the single buy order was executed on Chi-X Australia Pty Ltd.’s venue. The trade took place while Australia’s main venue was in the midst of its price discovery phase ahead of its closing auction. As quickly as the stock surged, it fell back, ending the session at A$33.84, a gain of 1.3 percent.

“It appears that a transaction occurred on the Chi-X market,” ASX said in an emailed statement, without elaborating. ASX transitions into pre-closing single price auction at 4 p.m. local time for a 10-minute period and then has its one-minute closing auction starting 4:10 p.m.

Chi-X Australia and BHP Billiton weren’t immediately available for comment.

Chi-X, which entered Australia in 2011, was created by Nomura Holdings Inc.’s brokerage unit Instinet to compete with incumbent exchanges. The value of shares traded at the venue averaged A$526 million ($375 million) a day in the week ended Oct. 5, according to ASX’s website. A daily average of A$3.8 billion worth of shares changed hands at ASX over the same period, the data show.

BHP’s London shares London rose 1.9 percent on Friday as of 10:42 a.m.

To contact the reporters on this story: Divya Balji in Singapore at dbalji1@bloomberg.net;Livia Yap in Singapore at lyap14@bloomberg.net

To contact the editors responsible for this story: Chris Nagi at chrisnagi@bloomberg.net, Teo Chian Wei, Sam Mamudi

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