Trading has resumed on the New York Stock Exchange after an outage of more than three hours caused by technical problems.

There was no interruption at the dozens of other U.S. stock exchanges Wednesday, including the Nasdaq, so investors were still able to buy and sell stocks easily.

The NYSE didn’t say what the problem was but described it as internal issue and not the result of a breach of its systems.

The market was already lower as traders worried about China’s failure to halt a plunge in its shares and talks remained stuck between Greece and its lenders.

In the last hour of trading the Dow Jones industrial average was down 210 points, or 1.2%, at 17,569. The Standard & Poor’s 500 index was off 25 points, or 1.2%, to 2,056.