Gracia Yancey Backer is out as head of the state's Employment Security Division.
A reporter calling her office Tuesday was told she no longer worked for the agency.
When asked if Backer had been released or had resigned, Gov. Jay Nixon's spokesman Scott Holste said the governor's office "won't be able to comment to that extent on personnel matters."
Backer did not answer calls to her New Bloomfield home seeking a comment for this story.
A Democrat, Backer headed the Employment Security Division from 2001-05 in Gov. Bob Holden's administration, and returned to the post after Nixon became governor in 2009.
Employment Security is a division of the state Labor and Industrial Relations department, and Backer's departure comes at the same time Nixon announced that Lawrence G. Rebman, the department director, was named an administrative law judge in Kansas City for the Worker's Compensation division.
"This move will enable Larry to continue serving the people of Missouri in an important position, while letting him return to his hometown," Nixon said Monday, in a news release. "I greatly appreciate what he has accomplished as a public servant so far, and take satisfaction in knowing that record will continue."
The governor named Julie Gibson, Workforce Development Division director since March 2009, as the Labor department's interim director.
Amy Susan, the Labor department's spokeswoman, didn't respond to an e-mail asking for a comment on Backer's situation.
Backer represented most of Callaway County in the state House of Representatives from 1983-2000.
She was majority floor leader in the 1997-98 General Assembly - the highest-ranking woman leader in House history, until Catherine Hanaway, R-Warson Woods, became House speaker in 2001.
Backer ran for lieutenant governor in the 2000 Democratic primary, but lost to state Sen. Joe Maxwell, D-Mexico, in a three-person race.