A recent article in The Wall Street Journal reports that over the past half a century, the Mormon Church “quietly built one of the world’s largest investment funds” now estimated at $100 billion, according to a whistleblower complaint filed with the IRS last year.

The complaint also alleged that the church has improperly used some of the funds housed in the investment arm called Ensign Peak Advisors, claims that have been denied by church officials. The article notes, however, that the complaint has “heaped pressure on the church to be more transparent about its finances,” something it has avoided for years.

The church established its investment arm in the 1960s with just three employees, during what was described as a period of financial hardship. By the late 1970s, the article reports, the division managed about $1 billion (according to the Sovereign Wealth Fund Institute) and in 1997 was spun off into Ensign Peak Advisors, a separate legal entity.

Interviews with former employee of Ensign Peak suggest that AUM reached between $80 billion and $100 billion as of last year, a level twice as large as Harvard University’s endowment and SoftBank’s tech-investment fund. Ensign’s holdings reportedly include $40 billion in U.S. stock, timberland in the Florida panhandle and investments in hedge funds such as Bridgewater Associates.

Roger Clarke, the head of Ensign Peak, claims that the holdings represent “rainy-day” funds to be used in tough financial times, explaining that the money will support the church’s work in poor areas of the world where members cannot tithe the 10% of annual income required by church members. Clarke said he believed church leaders were concerned that “public knowledge of the fund’s wealth might discourage tithing.”

According to Clarke, the fund invests conservatively using a “longer term horizon” than many other firms. “Among rank-and-file members of the church,” the article reports, “the whistleblower report unleashed an intense debate about tithing and how the church uses its vast resources.” But church officials maintain that most of Ensign Peaks funds “doesn’t come directly from tithing but from returns on investment.”