UPDATE 1-U.S. jobless claims jump, special factors blamed

(Adds details, remarks from Labor)

WASHINGTON, July 31 (Reuters) - The number of U.S. workers filing claims for new jobless benefits leapt 44,000 last week, Labor Department data on Thursday showed, but an official said the increase was at least partly due to special factors.

Initial claims for state unemployment insurance benefits rose to a seasonally adjusted 448,000 last week from a revised 404,000 the prior week, the Labor Department said. It was the highest reading since April 2003.

Analysts polled by Reuters had forecast 395,000 new claims versus a previously reported count of 406,000 the week before.

"Several states have indicated that they are experiencing increases in initial claims as an indirect result of the emergency unemployment compensation program," the Department said in a statement. He was referring to the federal extension of benefits for up to 13 weeks to ease the strain of joblessness as a weak housing market hurts growth.

States contacting people they thought would be eligible for extended benefits in fact found that many more than anticipated qualified for regular unemployment benefits, and as a result registered them as an initial claim, the Labor Department official said.

The official said the initial claims reading in the previous week may also have been influenced by this special factor, and initial claims over the next two weeks would also likely be affected. Many Americans who are eligible for unemployment insurance never bother to file a claim, he said.

The four-week average of new jobless claims, a better gauge of underlying labor trends because it irons out week-to-week volatility, rose by 11,000 to 393,000 from 382,000 the week before. This was the highest reading since October 2005.

This measure has risen steadily as the U.S. housing slump chilled growth and crimped hiring.

The number of people remaining on the benefits roll after drawing an initial week of aid jumped 185,000 to a much more-than-forecast 3.282 million in the week ended July 19, the most recent week for which data is available.

It was the largest weekly increase in so-called continued claims since June 1998.

Analysts expected continued claims to come in at 3.15 million. It was the 14th straight week that claims were above 3 million in a sign that the slowing economy is making it harder for U.S. workers to find jobs. (Reporting by Alister Bull; Editing by Neil Stempleman)