Vanguard Group, the No. 1 U.S. mutual fund company, on Friday took a step towards offering exchange-traded fund versions of dozens of its well-known actively managed mutual funds.

In a March 7 filing with the U.S. Securities and Exchange commission, Vanguard said it was seeking permission to issue active ETFs on existing funds.

These could include its Vanguard Explorer Fund, Vanguard Wellington Fund, bond index and municipal bond funds.

"No decisions have been made about which active funds, whether existing or to be created, will offer an ETF share class," Vanguard spokesman David Hoffman said.

He said Vanguard had been looking for some time at actively managed ETFs that can offer investors and advisers access to low-cost active management strategies.

Vanguard is the third-largest U.S. provider of ETFs that track a benchmark index of securities such as stocks, bonds or commodities.

The Valley Forge, Pennsylvania-based company had 67 ETFs with $345.5 billion in assets under management at the end of February.

Many active fund managers have been hesitant to launch ETF versions of their funds because of concerns that disclosing their portfolio holdings on a daily basis may reveal their strategies.

Several large asset managers, including BlackRock Inc., State Street Corp. and Eaton Vance Corp. have asked the SEC to let them market actively managed ETFs that would be permitted to report their portfolio holdings quarterly.

Hoffman noted that Vanguard would not offer shares of a fund "unless the fund's adviser reasonably believes that the daily disclosure of portfolio holdings would not have an adverse effect on the portfolio strategy and its execution."