Trading was delayed for almost two hours on Friday on the UK blue chip FTSE 100 and midcap stock indexes due to a technical glitch.

The London Stock Exchange said the outage was caused by a “technical software issue.”

Shares in the FTSE 100 and the FTSE 250 indexes began trading at about 9.40am London time, while other parts of the market opened as normal at 8am, according to a statement from London Stock Exchange.

“The impact to us is quite large as we are FTSE index traders and the futures are open,” John Moore, a trader at Berkeley Capital Wealth Management, told Bloomberg.

“Without seeing the underlying stock prices, it was difficult to know whether the futures price was ‘a true reflection of fair value on the FTSE’.”