(Portland, OR)  --  An investigation is underway into an incident in which several high school students were hospitalized after appearing to be under the influence of intoxicants.  Hillsboro School District officials emailed parents about the incident last night.  The email says four students at Hillsboro High School were taken to a hospital yesterday as a precautionary measure after allegedly showing signs of impairment.  Officials say it's not yet clear what sort of intoxicants the students allegedly ingested.