Fannie Mae said Thursday the rate for single-family home loans behind in payments by at least 90 days dipped slightly between February and March. But the rate of serious delinquencies for mortgages on apartment buildings worsened.

The government-controlled lender said its conventional single-family serious delinquency rate slipped to 5.47 percent in March from 5.59 percent in February.

For apartment building mortgages behind at least 90 days, the delinquency rate inched in March to 0.79 percent from 0.73 percent.

Fannie Mae and its sibling Freddie Mac were created by Congress to buy mortgages from lenders and package them into bonds that are resold to global investors. Together the pair own or guarantee almost 31 million home loans worth about $5.5 trillion. That's about half of all mortgages.