CNN  —  Fears are mounting of a potential environmental disaster off the coast of Britain after a cargo ship carrying toxic chemicals smashed into an oil tanker transporting jet fuel for the US military. The crash ignited a huge fire, which is still burning in the North Sea, about 10 miles off the coast of Hull, a busy port and fishing center. Dozens of people were rescued, but one crew member is unaccounted for, according to British authorities. Meanwhile, environmental groups have warned of