More borrowers who are timely on their mortgage payments are calling the Homeownership Preservation Foundation's Hope Hotline warning of future defaults.

HPF, a nonprofit that helps distressed borrowers through its hotline, says the number of callers who are current on their mortgages is up 70% this year. That trend is a bad sign since it suggests more homeowners are hanging by a thread and possibly heading for a real default.

Making matters worse, only 40% of hotline callers qualify for the government's Home Affordable Modification program.

"We are seriously concerned about the rise in homeowners who were classified as low risk when they took out their mortgages and, as a result of a combination of circumstances -- job loss, healthcare crisis and various recession-related issues -- have seen their economic situations severely deteriorate," said Colleen Hernandez, CEO of HPF. "This could result in the proverbial second shoe to drop for the housing crisis, especially considering the limited options available to homeowners who are struggling but not yet delinquent."

About 75% of the current borrowers calling in had credit scores above the subprime level when they first took out their loans. Today, those same homeowners are reeling from income reductions, higher credit card debts and eroding fiscal health, HPF said.

The report's takeaway is somewhat dire, although it shows borrowers taking proactive steps to save their homes.

"This foreclosure crisis is far from over," said Hernandez. "As lenders are learning to comply with new servicing standards set in place by the National Mortgage Settlement and the Consumer Financial Protection Bureau, make no mistake that notices of default are once again landing in mailboxes across the country at a pretty rapid clip."