Data on the U.S. unemployment rate for October may never be available after the weeks-long federal government shutdown, White House economic Adviser Kevin Hassett said Thursday as federal workers returned to work.

"The household survey wasn't conducted in October, so we're going to get half the employment report. We'll get the jobs part, but we won't get the unemployment rate. And that'll just be for one month," Hassett told Fox News' "America's Newsroom" program.

"We probably ... will never actually know for sure what the unemployment rate was in October," Hassett said.