WASHINGTON • The number of Americans filing new claims for unemployment benefits unexpectedly rose last week, boosted by surges in California and Virginia, but the underlying trend remained consistent with a steadily recovering labor market.

The second straight weekly increase in jobless claims reported by the Labor Department on Thursday puzzled economists. Some pointed a finger at the wildfires in California, while others blamed Hurricane Ida, which devastated U.S. offshore energy production in late August. There was little conviction that ongoing COVID-19 infections, driven by the highly contagious Delta variant of the coronavirus, were a factor.

“Some, but not all, of this recent pickup looks related to Hurricane Ida, as filings in Louisiana have been above their pre-storm trend in recent weeks,” said Daniel Silver, an economist at JPMorgan in New York.

“But even including any storm-related claims, the recent move up in filings has not looked particularly severe so far, and we don’t think the labor market recovery has been derailed at this point.”

Initial claims for state unemployment benefits increased 16,000 to a seasonally adjusted 351,000 for the week ended Sept. 18.

Economists polled by Reuters had forecast 320,000 applications for the latest week.

Unadjusted claims in California jumped 24,221 while Virginia reported a rise of 12,879. There were also notable increases in Oregon, Ohio and Kentucky.

Claims in Louisiana fell and have been above their pre-hurricane trend in recent weeks.

“Perhaps fires in California and the lingering impact of Ida in Virginia contributed to those increases, but we don’t know for certain,” said Nancy Vanden Houten, lead U.S. economist at Oxford Economics in New York.

“We expect claims to return to their downward path in the weeks ahead, but the data will be more uneven as claims get closer to pre-pandemic levels.”