Buoyed by expectations that higher interest rates are not an imminent scenario, investors are returning to some of the largest high-yield bond ETFs even as yields drop.

The iShares iBoxx $ High Yield Corporate Bond ETF (NYSEArca: HYG), the largest junk bond ETF by assets, pulled in $539 million worth of new assets last week, or almost 79%, of inflows to all bond ETFs over the same period, reports Sridhar Natarajan for Bloomberg.

Low interest rates are tempting investors to embrace riskier bonds in search of yield. Last month, the yield gap between junk bonds and U.S. Treasuries has narrowed, with the difference between Treasury yields and CCC-rated debt at 6.97 percentage points, the lowest since November 2007. [Investors Flock to Riskier Bonds, Debt ETFs]

Since May 28th, HYG and the SPDR Barclays High Yield Bond ETF (NYSEArca: JNK), the second-largest junk bond ETF, have pulled in $425.4 million and $41.5 million, respectively. Those inflows represent modest reversals of the outflows from the two ETFs earlier as investors moved into lower duration junk bond funds. HYG is still lighter by $1.6 billion this year.

According to Standard & Poor’s Ratings Service, default rates on low-rated corporate borrowers was 1.7% in April, slightly higher than the six-month low of 1.57% in March.

The actively managed AdvisorShares Peritus High Yield ETF (NYSEArca: HYLD) has seen its assets under management tally more than double this year. HYLD has pulled in $569.1 million in new assets, helping the ETF enter the $1 billion in AUM club, as investors have warmed to the fund’s lower duration but still meaty yield. [Peritus High-Yield ETF Tops $1B in AUM]