The number of people who failed to pay their mortgage last month rose to its highest level since 2011.

In May, 4.3 million homeowners missed their mortgage payments, up from 2 million at the end of March, according to Black Knight, a mortgage data company. That brings the overall delinquency rate for May to 8%.

The rate includes borrowers who have arranged to delay or defer their mortgage payment by entering into a forbearance program with their loan servicer, as well as homeowners who have missed payments without such protection. Those in forbearance are protected from being noted as delinquent in their credit report and are expected to work with their lender to arrange a repayment plan.

But it is not likely everyone in forbearance will ultimately be able to pay back what they owe and banks and housing industry experts are keeping a close eye on the delinquency numbers to ascertain how many people are falling behind, whether they are in forbearance or not.

The report shows that serious delinquencies are increasing, up more than 50% over the past two months, with 631,000 homeowners now 90 days or more past due. But Black Knight’s tracking of mortgage payments on a daily basis shows that already a higher share of payments have been made in June than by this point in May, suggesting the delinquencies may be leveling off.

Many homeowners who entered into a forbearance program that allowed them to delay their payment still made their regular payment over the past few months, the research showed, although the share that are still making payments is dropping. In April, just under half of people in forbearance made their regular monthly payment. By the end of May, that number had fallen to a little more than a quarter. By June 15, only 15% had made their payment.

The states with the highest percentage of loans that aren’t current are Mississippi – with a delinquency rate of 13%, Louisiana at 12%, followed by New York, New Jersey and Florida, all at 11%.

The next step following serious non-payment is typically foreclosure. But moratoriums on foreclosure and the forbearance programs, which keep homes from being foreclosed on while homeowners are in the program, mean that foreclosure levels are at record lows – for now. The share of homeowners in active foreclosure is the lowest it’s been since Black Knight began tracking 20 years ago.