FILE PHOTO: A sign marks a Fidelity Investments office in Boston, Massachusetts, U.S. September 21, 2016. REUTERS/Brian Snyder

(Reuters) - Fidelity Investments, one of the world’s largest investment managers, said on Tuesday it had expanded its commission-free exchange traded fund (ETF) platform to include more than 500 ETFs.

The expansion is a part of Fidelity's partnership with asset manager BlackRock Inc, the company said bit.ly/2BzXqu6 in a statement.

Poor performance of asset managers towards the end of 2018 prompted investors to withdraw cash from actively managed institutional funds in the fourth quarter, but people parked record cash in the company’s low-cost exchange traded funds.

Earlier in the day, another investment manager, Schwab, said it would also double its ETF lineup and add iShares ETFs to its offering.

Schwab clients will be able to buy and sell 503 ETFs, starting March 1, the company said in a statement.

Fidelity has more than $6.7 trillion of assets under management, including $380 billion in ETF assets, and currently serves more than 13,000 institutions.

The platform will offer ETFs from over ten asset managers, including iShares ETFs.