Trading on the London Stock Exchange has been suspended since markets opened on Friday, due to electronic trading system problems.
Every minute of halted trading causes millions of pounds worth of lost trades. The exchange is still down, as of 10:20am.
Trading has been halted and nothing is taking place on the market, a London Stock Exchange (LSE) spokeswoman told ZDNet UK.
Trading halted at the London Stock Exchange, due to a glitch.
"At three minutes past 8:00am we put the market into a pause phase which meant that no continuous trading was taking place," she said. "We're still investigating this."
The market is in a "hold phase", the spokeswoman said.
"Participants can continue to delete but not enter orders at this time and no automatic execution is taking place," the LSE Group said in a statement on its website at 8:59am. "All market maker quotes are indicative only."
The problems occurred in the LSE's SETS and SETSqx systems. SETS — Stock Exchange Electronic Trading Service — is the LSE's "flagship electronic order book," according to its website, while SETSqx provides a trading platform for securities less liquid than those traded on SETS.
The LSE is working to fix the problem, the spokeswoman said, but could not give an indication of when the market would restart.
SETS and SETSqx run on a SUSE Enterprise Linux trading platform. The LSE's main cash markets migrated to the platform, called Millennium Exchange, on 14 February.
The migration has been dogged by problems — on 17 February some share brokers were not able to display current prices for shares and on Thursday the LSE's derivatives platform experienced further technical problems.
The LSEG reports that continues trading resumed in the market at 12:15pm.
However, the group will not extend the LSE's trading hours to compensate for the morning's disruption.
"We sincerely regret the inconvenience that today's disruption to trading has caused our customers," Xavier Rolet, chief executive of the LSEG said in a statement. "We have resolved the real time data dissemination issue and our UK cash equity markets have now resumed trading."