(Reuters) -The U.S. Securities & Exchange Commission told Reuters that it was "unclear" whether the dozens of recent filings by asset managers to issue highly leveraged ETFs would be approved by the agency.

Since the U.S. government shutdown began, "the agency has received a large number of registration statements for ETFs seeking to offer 3x and 5x leveraged, equity-linked exposure," said Brian Daly, director of the SEC's division of investment management. 

"It is unclear whether these ETFs would comply with the Derivatives Rule (Rule 18f-4), which generally limits leverage to 2x."

On Wednesday, ETF issuer Volatility Shares filed to launch a total of 27 highly leveraged ETFs, including the first-ever proposed 5x ETF for the U.S. market, in a move that raised eyebrows amid widespread concerns over inflated asset prices.

A 5x target means that an ETF would seek to quintuple the daily return of an underlying single stock. Until now, the SEC has approved single-stock leveraged ETFs with a maximum of 2x.

A Reuters analysis of SEC filings found that Volatility proposed its filings to go effective 75 days after submitting. Such time-based flipping of filing status has previously been used by companies looking to IPO during a shutdown as well.

SEC staff will not be able to review the new filings until after the  shutdown is over, Daly added.

Volatility did not immediately respond to a Reuters request for comment.