The number of new claims for unemployment benefits rose again last week, increasing by 1,000 to 497,000, the Labor Department reported Thursday.

The gains boosted the four-week moving average of new jobless claims to 474,000, up 11,500 from the previous week.

Officials blamed Hurricanes Gustav and Ike for adding at least 45,000 claims. The largest increases in new claims last week were reported in Louisiana and Texas, the two regions most affected by the storms. The largest decreases were in Kansas and South Carolina.

Excluding the storms, the report shows an underlying trend of approximately 450,000 new jobless claims. Ian Shepherdson, chief economist for High Frequency Economics, a New York-based research firm, called that “disconcertingly high.”

Excluding the period after 9/11, claims filed in 2001 peaked at 400,000, Shepherdson said.

The Labor Deparment’s report on non-farm payrolls and the unemployment rate for September will be released on Friday.