March 25 (UPI) -- Environmental organization Oceana has accused the Mexican government of maintaining an opaque response to an oil spill that has affected at least 390 miles of coastline in the Gulf of Mexico. The oil has largely impacted the southern part of Veracruz state and the northern part of Tabasco state since early March, with dozens of contaminated sites still not receiving attention. The spill has lasted nearly three weeks without an identified cause or confirmed responsible parties,