NEW ORLEANS -- Fresh off a 10-nation tour and facing a federal investigation into his handling of public library donations, Grammy-winning trumpeter Irvin Mayfield has resigned as a professor at the University of New Orleans.

Meanwhile, WWL-TV — which reported in May that Mayfield and his business partner, Ronald Markham, had changed the rules of the city's public library support foundation to steer at least $863,000 to their Jazz Orchestra — found archived city documents indicating that the Jazz Orchestra took a portion of a $125,000 grant for organizing the grand opening of the Mahalia Jackson Theater for the Performing Arts and used it to pay its musicians for a Jazz Fest concert and for recording the album that won the Grammy.

Before he resigned from UNO, Mayfield had been making $63,000 a year from the cash-strapped public university to teach two courses and head up the school's New Orleans Jazz Institute. That has no relation to Mayfield's New Orleans Jazz Orchestra, a private nonprofit, but NOJO's director of programming, Stephanie Mayne, also received a $45,000 salary from UNO to serve as Mayfield's university assistant. That's more than some professors make.

UNO's dean of Liberal Arts, Kevin Graves, said both Mayfield and Mayne resigned voluntarily last week, two weeks before fall classes were to begin. Graves said the university did not pressure them to resign, even though the university just underwent millions of dollars in forced cuts. Government watchdog Rafael Goyeneche questioned whether the school could afford Mayfield's salary in a WWL-TV report in May.

Mayfield, who does not have a college degree, has been teaching a humanities class called "New Orleans as Discourse" as well as a music class. Seven students had signed up for the humanities class but nobody had registered to take the music class, said Charles Taylor, director of the music department.

Mayfield resigned due to "scheduling conflicts," according to a statement from NOJO spokesman Malcolm Ehrhardt. He said the UNO Jazz Institute would continue to offer free Saturday music school, jazz summer camps and commission works from UNO professors, in spite of Mayfield's departure. Graves, however, said the Jazz Institute's future has not yet been determined by university leadership.

Graves said Mayne was hired by a selection committee, which interviewed several candidates after publicly advertising the position of Mayfield's assistant. He did not comment on the fact that she also works for Mayfield's orchestra.

WWL-TV has been seeking answers for months about NOJO's use of the grant for the Mahalia Jackson Theater opening. Ehrhardt's statement Monday reiterated the nonprofit's previous position that it is taking questions seriously but will not comment until an internal investigation into its finances is complete.

The records in the City Archives show that in December 2008, then-Mayor Ray Nagin, Mayfield's political patron, awarded NOJO $125,000 to run grand opening ceremonies for the Mahalia Jackson, which reopened with fanfare in January 2009.

The money was the first of several grants Nagin gave NOJO from the Wisner Foundation, which donates money each year which the mayor of New Orleans can use for grants to nonprofits and public entities for beautification, education, recreation or human services.

NOJO spent $101,731 of its grant to pay a ballet company, a public relations firm, a graphic designer and musicians — including Irma Thomas, Jeremy Davenport and the NOJO band itself — for participating in the event. But records from 2010 also show that the $23,269 left over was used to pay its own musicians for two unrelated performances in 2009: the recording of the Book One CD that won a 2010 Grammy Award, and a Jazz Fest concert.

After a series of stories by WWL-TV in May, Mayfield canceled several public appearances and was uninvited from the kickoff of the city's tricentennial celebration, although the invitation promised he would perform and the event was held at NOJO's Jazz Market, where a huge image of Mayfield hangs on the wall.

Mayfield and NOJO then embarked on a 10-nation tour of Europe, Australia, South America and Canada. His first show back at Irvin Mayfield's Jazz Playhouse at the Royal Sonesta Hotel was last week. WWL-TV again tried to interview him, but he slipped out a side exit. Asked why he wouldn't answer questions about the NOJO money, Markham shouted, "I have no answers for you, sir!"

Bill Summers, who helped give Mayfield his first big break with Los Hombres Calientes in the 1990s, said the music community has been rocked by the revelations and Mayfield needs to stop avoiding the issue.

"If you really, really care about what's going on in the community, the house is on fire. Then you put the fire out. But you can't find him. The fire chief is missing," said Summers, who said Mayfield and Markham forced him out of Los Hombres Calientes after the group won a Billboard Award. "If it were I, I'd be in the street, confronting the people or talking and explaining myself, and/or apologizing."