MANKATO — Gas prices have hit a new record with Minnesota average prices at $4.23 per gallon Friday. Mankato gas stations were selling at $4.19 a gallon.The state average tops the record of $3.98 per gallon posted in 2008.The sudden spike in gas prices has been blamed on the maintenance closures of several refineries in the Midwest.The price jump prompted Minnesota Sens. Amy Klobuchar and Al Franken to send a letter to Secretary of Energy Steven Chu on Thursday urging him to examine the timing of the closures. They said they want to find ways to avoid multiple closures like this in the future.Analysts predict prices will continue to rise over the next few weeks. Relief isn't expected until June. Minnesota had the second-highest gas prices in the nation this week, topped only by Hawaii.