I know it looks like nothing much happened in the U.S. stock market today, Thursday, September 6. After all the Standard & Poor’s 500 stock index was off just 0.37% and the Dow Jones Industrial Average was actually head by 0.08%.

But below the surface, there was increased weakness today that leaves me concerned.

We had a continued sell off in technology names–both the big stars like Amazon (AMZN), down 1.83% on the day and Facebook (2.78%) and chip stocks in general on worries over demand. This technology weakness follows the pattern that I called profit-taking after yesterday’s session.

But today we also had energy stocks and financial stocks joining in with the Financial Select Sector SPDR ETF (XLF) falling 0.46%. This suggests that the weakness in the U.S. market is expanding from profit taking in the big technology names. (Although more tech names joined the retreat today with Apple (AAPL), for instance, down 1.66%.)

Today’s action also suggests increased weakness in the U.S. market because emerging markets had a relatively good day for a change. The iShares MSCI Emerging Markets ETF (EEM) inched ahead 0.1%. ETFs for Brazil and Argentina were higher by 1.76% and 1.98%, respectively.

A continued rout in emerging market stocks wasn’t the key driver today for the U.S. market weakness.

I’d also draw your attention to a change in the buy/sell action in the Standard & Poor’s 100 stock index. As Don Kaufman at TheoTrade reported last night,  yesterday the S&P 100 fell even though the number of advancing stocks exceeded the umber of declining issues by 61 to 39. That’s because big cap stocks such as Amazon, Facebook (FB), and Alphabet (GOOG) were all down, taking the index with them.

Today, on the other hand, by my preliminary count 54 stocks in the index were down (or flat) against just 46 winners. That’s a reflection that the financial and energy sectors joined technology to the downside today. And it suggests that the weakness in the U.S. market is spreading beyond profit taking among the tech giants.

One day does’t a trend or a trend reversal make, of course.

But I would note that weakness in U.S. stocks on a day when emerging markets didn’t fall isn’t a good sign because there is no reason to think that the emerging market crisis is over. The crisis has been driven by a rising dollar, climbing U.S. interest rates, and fears of slowing global growth as a result of the effects of a tariff war. Those reasons for the emerging market crisis haven’t disappeared and they are not likely to for a while. Which suggests that U.S. markets will have more opportunity to feel nervous in the days ahead.