CME Group said technical issues had shut down contracts on its Globex electronic trading system on Tuesday afternoon with primarily agricultural and grains contracts affected and no impact on oil or metals.
Trading continued in the open outcry pits on the floor of the Chicago Board of Trade. Shutdowns on the electronic trading system are rare.
"We can confirm that we are experiencing technical issues ... we are working to get this resolved," CME spokesman Chris Grams said.
CME said all grain futures and options currently halted on CME Globex will be settled Tuesday via open outcry methodology.
A trader on the floor said the market was "in a panic'' due to the shutdown of the electronic system, which handles more than 90 percent of the volume on a typical day.
The CME Globex trading systems went down at approx 1:50 p.m. ET, about 25 minutes before the market close.
Wednesday is a big day as USDA monthly crop reports are due out midday. That report is supposed to show new demand reports that the market is expecting.
It's important to note that while trading on certain parts of the Globex electronic platform was halted, trades continued to be executed and the market was to be closed in open outcry trading.