More than a fifth of US mortgage holders owed more than their homes were worth in the first quarter as repossessions climbed to a record, according to Zillow.com. Twenty-three percent of owners of mortgaged homes were underwater during the period, up from 21% in the previous three months, the Seattle-based property data provider said today in a report. More than one in 1,000 homes were repossessed by lenders in March, the highest rate in Zillow data dating back to 2000. Underwater homes are more likely to be lost to foreclosure because their owners have a harder time refinancing or selling when they fall behind on loan payments.