NEW YORK: Trading in all securities were halted on the New York Stock Exchange on Wednesday following earlier reports of technical difficulties, although NYSE-listed issues were still trading on other exchanges.

The outage comes on the same day as United Airlines grounded planes at US airports for an hour due to a computer glitch. The website for the Wall Street Journal newspaper was also suffering intermittent glitches.

After the halt, US stocks extended their losses, but in low volumes, with the S&P 500 hitting a session low and the Dow Jones Industrial Average and Nasdaq both falling more than 1 per cent.

“It's under control. We're just waiting for word. There's no sign of panic at all,” Mark Otto of J. Streicher & Co in New York said from the NYSE floor.

“We're waiting to hear word on if there's going to be a reopening, and when it is or any more details.” US markets were in the red even before the halt, which started just after 11:30 a.m. ET, as the slide in Chinese markets spurred concerns over its impact on global economic growth.

“We will be providing further updates as soon as we can, and are doing our utmost to produce a swift resolution, communicate thoroughly and transparently, and ensure a timely and orderly market reopen,” a spokeswoman for the exchange operator said in a statement.

The stocks continue to trade on other exchanges, such as those run by Nasdaq OMX Group and BATS Global Markets.

Meanwhile, the US Department of Homeland Security said there were “no signs of malicious activity at this time” relating to technical difficulties that halted trading at the New York Stock Exchange and an earlier technology problem at United Airlines that had grounded flights, CNN reported on Wednesday.