U.S. mortgage rates increased slightly last week, the first gain since last month, according to data released Tuesday by Zillow.com.

The average rate for a 30-year fixed mortgage last week was 5.07%, up from 4.96% the prior week, according to the Seattle real estate Web site operator's Mortgage Rate Monitor.

The biggest gain for 30-year mortgages was in Illinois, which increased to 5.28% from 5.07%. Illinois also had the highest rate, followed by Virginia's 5.18%. The lowest rates were in Georgia, with 4.92%, and in Arizona, with 4.85%.

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