Investors poured $16.9 billion into exchange-traded funds in March, bringing the first-quarter total to $53.1 billion, according to data from Morningstar.

Despite outflows of $8.1 billion from SPDR S&P 500 SPY, U.S.-stock ETFs gained $11.2 billion—the most of any asset class. Fixed-income ETFs also pulled in $4.8 billion.

Commodities and international stock were the only asset classes that saw outflows in March. Investors pulled $4.1 billion from diversified emerging-markets ETFs in March, their first monthly outflow since May 2012.

At the firm level, Vanguard continued to gain market share, leading all ETF providers for the month and the quarter. Its market share increased to 19% from 17% one year ago.