New York-based Warburg Pincus is set to take a majority stake in Santa Ana-based Universal Services of America Inc.
The investment values Universal Services at about $1.5 billion, according to reports.
Universal Services provides security and janitorial services. It is among the largest security companies in the U.S. and one of the largest employers in Orange County, with about 3,600 employees locally and 50,000 overall.
The company, headed by Chief Executive Steve Jones, is currently backed by Zug, Switzerland-based global investment manager Partners Group, which made an equity investment in Universal Services in 2013.
Universal Services has about $1 billion in annual revenue.