Oil gushed largely unchecked from BP's ruptured Gulf of Mexico well on Wednesday after a collision involving an undersea robot halted efforts to contain the worst oil spill in U.S. history.

NEW ORLEANS—About 88,200 gallons (333,873 litres) of oil have leaked from a Shell flow line into the Gulf of Mexico about 90 miles off the coast of Louisiana, the U.S. Coast Guard has said.

The Gulf of Mexico’s white sandy beaches are a draw for tourists, and as the busy Fourth of July holiday approaches, officials are hoping beachgoers will take extra precaution.