The number of Americans filing initial claims (search) for jobless aid unexpectedly plunged 48,000 last week, the largest drop in more than three years, according to a government report on Wednesday that suggested job market conditions may be improving.

Just 319,000 first-time claims for state unemployment benefits (search) were filed in the week ended January 15, the Labor Department (search) said. Wall Street economists had expected claims to move down to 345,000 from the 367,000 reported for the prior week.

A Labor Department analyst said there were no special factors to account for the unexpectedly large decline, but said it was hard to adjust the data for seasonal quirks around the holiday season.

The drop brought the four-week moving average of initial claims down 3,000 to 341,000, sticking close to levels it held for much of last year. Economists watch the average closely because it smooths out week-to-week volatility to provide a better gauge of underlying job market trends.

Another labor-market barometer in the report, the number of Americans still on the benefit rolls after receiving an initial week of aid, rose by 47,000 to 2.69 million in the week ended January 8, the most recent data available. While these so-called continued claims increased, the rise followed an unusually large drop of 209,000 a week earlier.