Washington (CNN Business) The US economy added 304,000 jobs in January, a surprisingly strong month of hiring as employers continue to bring in new workers.

January was the 100th straight month of job gains. The Labor Department said the government shutdown that lasted more than a month had "no discernible impacts" on hiring and wages, but it did contribute to the uptick in unemployment. The unemployment rate rose slightly to 4%.

Another possible ripple effect from the shutdown: The number of people working part time for economic reasons jumped by about 500,000, after many months of declining. The Labor Department said that increase might be attributable to private-sector contractors who lost work during the lapse in funding.

Some of the unexpectedly large jump in hiring appeared to have been pulled forward from December, which was revised down from 312,000 jobs to 222,000. Still, the average for the last three months is now 241,000 jobs — which represents an acceleration in job growth, not a slowdown, as many have been predicting.

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