The New York Stock Exchange suspended trading in all stocks Wednesday morning.

The NYSE halted stocks at 1532 GMT, saying in a notice on its website that "additional information will follow as soon as possible." An NYSE statement cited "technical issues," CNBC reported.

The Department of Homeland Security said that there is "no sign of malicious activity" at the NYSE, meaning no indication so far of a cyber attack, CNN reported.

"We're currently experiencing a technical issue that we're working to resolve as quickly as possible. 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 re-open," the NYSE said.

It appears that all other exchanges, including the Nasdaq, are still operating. That means investors can still trade, just not on the NYSE.

The Wall Street Journal's website is also not working. It stopped functioning around the same time that the NYSE went down. 

Earlier in the day Wednesday, certain NYSE stock symbols halted trading due to a technology glitch, but that seemed to have cleared. The exchange says there is more information to come.

"They've been having problems all day. They seemed to have rectified it earlier and then it happened again. Now they shut it all down," said Joe Saluzzi, co-head of trading at Themis Trading and author of Broken Markets.

US markets were already down Wednesday.

The Dow was down 175 points (about 1 percent) around the time of the halt. The losses have since deepened.