SAN DIEGO — The Marine Corps says 86 recruits are now being treated after hundreds at a San Diego boot camp fell ill with symptoms indicating they were exposed to E. coli — bacteria that signal the presence of fecal matter.

More than 300 recruits out of 5,500 in training have fallen ill as the military branch prepares for a graduation ceremony Friday for more than 500 new Marines.

The military said Thursday 16 of the 86 were at an off-base medical facility. The rest remained on base.

As a precaution, any Marine who previously showed symptoms — including diarrhea, stomach cramps, fever and vomiting — will remain under observation.

The military says it will help recruits make up missed training to remain on track. Some graduation dates may be changed.