U.S. equities fell at midday as sliding tech shares slowed the recent record-setting stock runup. The Dow Jones Industrial Average, S&P 500, and Nasdaq were all lower.

Nvidia (NVDA) shares dropped when Chinese officials began an investigation of the chipmaker for possible monopolistic practices.

Shares of Omnicom Group (OMC) slid after the advertising giant announced it was purchasing rival Interpublic Group (IPG) for $13 billion, creating the largest ad conglomerate. Interpublic Group shares took off.

Comcast (CMCSA) shares sank as the cable and broadcast company said it expects to lose more than 100,000 broadband subscribers in the current quarter.

Hershey (HSY) was the best-performing stock in the S&P 500 on a report Mondelez International (MDLZ) was considering acquiring the chocolate maker. Mondelez shares tumbled.

Shares of Super Micro Computer, or Supermicro (SMCI), gained after the troubled server maker reported that the Nasdaq had delayed a possible delisting of the company from its index until Feb. 25. That gave Supermicro more time to file its annual report, which has been held up because of accounting concerns.

Enphase Energy (ENPH) shares gained when the solar power firm announced a collaboration agreement with NextEnergy in the Netherlands.

Oil and gold futures rose. The yield on the 10-year Treasury note was higher. The U.S. dollar was up on the yen, but lost ground to the pound and was little changed against the euro. Most major cryptocurrencies traded lower.