September's jobs data arrived with a thud Wednesday: 18,400 jobs lost, the first monthly loss since August 2010 and the most since early 2009.

State officials cautioned that the estimate likely would be revised as more complete data become available. They also noted that the unemployment rate fell in September to 9.1 percent, down from 9.3 percent in August.

About 10,800 of the jobs lost were in government, mainly in K-12 and higher education as budget cuts took effect.

Job losses in the private sector were distributed broadly across many industries, officials said, but the restaurant industry suffered the most, slashing 3,700 jobs.

September's initial estimate of job losses hearken back to the depths of the Great Recession — when the state economy was hemorrhaging 20,000 jobs a month.

"We probably lost some jobs last month, but not as many as the preliminary data suggest," said Greg Weeks, the director of the state's Office of Labor Market & Economic Analysis.

Case in point: In August, the state initially reported 3,800 jobs gained. On Wednesday, officials revised that number to a gain of 6,700 jobs, with the leisure and hospitality sector and the trade, transportation and utilities sector seeing the biggest gains.

September's report of job losses, derived from a survey of establishments, clashes with the falling unemployment rate, which is estimated from a separate household survey.

From the household survey, officials estimate that unemployment fell slightly statewide and the number of people with jobs grew.

For months the two surveys — both are conducted by the federal Bureau of Labor Statistics — have been producing opposite signals about the labor market.

"It's not unusual for the surveys to generate somewhat different results, but the gap between the two September surveys is much larger than we usually see," Weeks said.

In the Seattle metropolitan area, the unemployment rate fell to 8.6 percent from 8.9 percent in August.

Statewide, only three sectors showed job gains in September: manufacturing was up by a net 800 jobs (with the aerospace subgroup up 1,000); education and health services, up 600; and professional and business services, up 100.

Most sectors lost ground: Leisure and hospitality was down 3,400 jobs; construction, 1,800; information, 1,100; transportation, warehousing and utilities, 900; wholesale trade, 900; other services, 500; financial activities, 200; and retail trade, 200.

Over the past 12 months, the state's economy gained a net 27,300 jobs; the private sector added 44,600 jobs, but that was offset by a loss of 17,300 government jobs.

The state estimated 317,594 people in Washington were unemployed and seeking work in September. Nearly 203,000 received $229 million in jobless benefits.

As of Oct. 8, 62,229 Washington workers had exhausted all unemployment benefits, officials said.

Sanjay Bhatt: 206-464-3103 or sbhatt@seattletimes.com