The NASDAQ stock exchange unexpectedly halted all trading on its platform Thursday following a technical problem.

The nation’s second-largest exchange told traders early Thursday afternoon that it was freezing activity “until further notice.” The stock exchange said it was dealing with a problem with the data feed that provides stock quotes.

A spokesman for the Securities and Exchange Commission said the agency is “monitoring the situation and are in close contact with the exchanges.”

Treasury Secretary Jack Lew has also been briefed on the matter and is receiving updates, according to a Treasury official.

The apparent technical glitch brought a screeching halt to the trading of the some of the nation’s most high-profile stocks, including Apple, Netflix and Microsoft.