OppenheimerFunds’ Dan Loughran, who oversees $24 billion of municipal-bond funds for the firm, will step down at the end of September after a decade leading a group known for aggressive bets on high-yield state and local-government debt.

Loughran, 52, started with the firm’s Rochester funds in 1994 when it was an independent company and has led the group since 2006. He has shifted to an advisory role to help Chief Investment Officer Krishna Memani with the transition, OppenheimerFunds said in a statement. Portfolio managers Scott Cottier and Troy Willis were appointed co-heads of the municipal-bond group.

OppenheimerFunds is known for its strategy of plowing cash into the most high-risk corners of the $3.7 trillion municipal market in pursuit of big returns. Over the years, its funds have invested in tobacco bonds, real-estate development deals roiled by the housing-market crash and debt issued by Puerto Rico. Its high-yield fund returned more than 14 percent over the past year, beating 98 percent of its peers, according to data compiled by Bloomberg.

“Throughout his career, Dan has been instrumental in helping the Rochester funds and their shareholders navigate the muni markets and find long-term value through active management,” the company said in a statement.

OppenheimerFunds successfully sued Puerto Rico to block a law that would have allowed some agencies to reduce their debt in court, much like a municipal bankruptcy.

Loughran’s departure comes after the firm’s case prevailed at the Supreme Court and President Barack Obama signed legislation that will allow for a broad restructuring of the Caribbean island’s debt under the oversight of a federally appointed board. That makes it an “opportune time” for Loughran to hand off his duties, the firm said.