Refinancing continued to rebound in March, with refinances accounting for 25% of all mortgage rate lock activity, according to a report released Tuesday by Optimal Blue. That is the largest share of refinances since September of last year.

Overall rate lock volume in March was up 24% month over month, driven by a surge in early spring buyers and existing homeowners looking to refinance at lower rates. The 30-year conforming mortgage rate ended the month at 6.6%, the same as February, according to Optimal Blue.

Purchase loan volume rose 21% in March, though it was down 2% from the prior year. But rate-and-term refinances leaped 52% and cash-out refinances were up 20% from the previous month.

“March brought a notable shift in borrower behavior,” said Brennan O’Connell, director of data solutions at Optimal Blue, in a statement. “Refinances made up a quarter of all lock activity for the first time in six months, and we saw a clear rise in nonconforming loan share as buyers looked for more flexible options and higher loan amounts. These are key indicators that consumers are actively adapting to the current rate environment.”

Nonconforming loans, which includes jumbo and non-qualified mortgages, comprised 16.8% of total rate lock volume, up from 15.5% in February. Conforming loan share had a 1% month-over-month decline to 51%.

Though Optimal Blue did not provide a data point for February, the company said it observed an increase in adjustable-rate mortgages in March, which it links to growing demand for nonconforming loan options among buyers seeking affordability.

Optimal Blue reported that the average home purchase price was $486,900 in March, up from $480,200 in February. That resulted in a corresponding increase in the average loan amount, which rose from $380,500 to $391,700 last month.