NEW ORLEANS — After securing a new, tight-fitting cap on top of the leaking well in the Gulf of Mexico, BP prepared Tuesday to begin tests to see if it will hold and stop fresh oil from polluting the waters for the first time in nearly three months.

NEW ORLEANS — Robotic submarines removed the cap from the gushing well in the Gulf of Mexico on Saturday, beginning a period of at least two days when oil will flow freely into the sea.