Employment vacancies at U.S. businesses unexpectedly surged in August, a sign that the Labor Market Remains tight and robust despite the Federal Reserve’s efforts to slow the economy.

Job openings totaled 9.61 million for the month, a jump of nearly 700,000 from July and well above the Dow Jones estimate for 8.8 million, the Labor Department said Tuesday in its monthly Job Openings and Labor Turnover Survey.

Hires, however, rose only modestly, moving up to 5.857 million, an increase of just 35,000.

Much of the increase in openings came in professional and business services, which showed a burst of 509,000.

Stocks fell following the report as a tighter Labor Market could put more pressure on the Fed to keep interest rates elevated. The Dow Jones Industrial Average most recently was off more than 260 points on the session.

The Fed follows the JOLTS report closely for signs of labor slack.

Openings had been on the decline for the last several months, indicating that the central bank’s interest rates hikes were beginning to have an impact on a labor market that had been hit by a large supply-demand mismatch in which openings had outnumbered available workers 2 to 1. The ratio now is down to 1.5 to 1, following an increase of workers classified as unemployed in August.

The August JOLTS report comes just a few days ahead of the department’s nonfarm payrolls count for September. Economists surveyed by Dow Jones expect that report, due Friday, to show an increase of 170,000.

Quits, a measure of worker confidence in finding a new job after leaving a previous position, were little changed. That also was the case with total separations and layoffs.