The number of Americans filing for unemployment benefits increased less than expected last week, suggesting the labor market continued to tighten after recent hurricane-related disruptions.

Initial claims for state unemployment benefits increased 10,000 to a seasonally adjusted 233,000 for the week ended Oct. 21, the Labor Department said on Thursday. Claims fell to 223,000 in the prior week, which was the lowest level since March 1973.

Economists polled by Reuters had forecast claims rising to 235,000 in the latest week. They have declined from an almost three-year high of 298,000 hit at the start of September in the aftermath of Hurricanes Harvey and Irma, which ravaged parts of Texas and Florida.

The impact of Harvey and Irma has largely dropped out of the data for the mainland United States. But Irma and Hurricane Maria continue to impact claims for the Virgin Islands and Puerto Rico, now virtually isolated because of the destruction of infrastructure due to the storms. A Labor Department official said they continued to estimate claims data for the islands.

Last week marked the 138th straight week that claims remained below the 300,000 threshold, which is associated with a strong labor market. That is the longest such stretch since 1970, when the labor market was smaller. The labor market is near full employment, with the jobless rate at more than a 16-1/2-year low of 4.2 percent.

The four-week moving average of initial claims, considered a better measure of labor market trends as it irons out week-to-week volatility, fell 9,000 to 239,500 last week. That suggests a sharp rebound in job growth in October after nonfarm payrolls dropped by 33,000 jobs in September.

The claims report also showed the number of people still receiving benefits after an initial week of aid declined 3,000 to 1.90 million in the week ended Oct. 14, the lowest level since December 1973.

The four-week moving average of the so-called continuing claims fell 4,500 to 1.90 million, the lowest reading since January 1974. The continuing claims data covered the week of the household survey from which October's unemployment rate will be derived.

The four-week average of continuing claims fell 40,500 between the September and October survey weeks, suggesting a further improvement in the unemployment rate as labor market slack continues to diminish.