NFL franchise San Francisco 49ers have increased their stake in Leeds United to 37 percent, the Premier League club announced on Monday.
Leeds owner Andrea Radrizzani has overseen a resurgence in the club's fortunes since taking a controlling stake in 2017 -- including a return to the Premier League this season after a 16-year hiatus.
The 49ers, who are five-time Super Bowl champions, bought an initial 15 percent stake from Radrizzani in 2018.
Paraag Marathe, the president of 49ers Enterprises, who was already a member of the Leeds board, becomes vice-chairman.
Leeds said Marathe would be more involved in decision-making and day-to-day operations.
"Our 49ers Enterprises team has always shared Andrea's vision for constructing a powerful and winning club in the most competitive football league in the world," said Marathe in a statement on the Leeds website.
"The experience of the last three seasons has been more exhilarating than we could have ever imagined."
Radrizzani has won praise for stabilising the club after taking over from fellow Italian Massimo Cellino.
He persuaded Argentine coach Marcelo Bielsa to become manager in 2018, which proved pivotal to their return to the Premier League.
"The hard work and bold leadership demonstrated by Andrea and his talented team has restored Leeds United's rightful place in the Premier League," said Marathe.
"We look forward to playing an even bigger role in supporting their efforts to climb the table this year and into the future."
Radrizzani said the 49ers fitted the mould of investor he wanted at the club.
"I have always been open to bringing partners on this journey with me, as long as these actions can benefit the long-term strategy of the club," he said.