U.S. Commerce Secretary Gary Locke will tour a federal lab in Mississippi where seafood caught in the Gulf of Mexico is being tested to determine if it is tainted by oil.

The National Oceanic and Atmospheric Administration lab is the first stop for seafood being prepared for analysis as federal officials determine which areas of the Gulf should be reopened to commercial fishing after BP PLC's April 20 oil rig explosion began a massive oil spill. Locke will tour the site on Tuesday afternoon.

About 26,287 square miles of federal waters remain closed. At the height of the spill, about 37 percent of federal waters in the Gulf were closed, or 88,522 square miles. NOAA officials say seafood caught in all the reopened areas is safe to eat.