At first it was a chemical spill that put four adults in the hospital.  Now, it is inconclusive.

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Dr. Virginia Caine with Marion County's Health Department says the tests came back negative.  They tested for numerous chemicals that could have been used and none of them were found on samples collected yesterday after 7 people fell ill in the Riley Hospital at IU Health emergency room.

Dr. Caine says there's a possibility that we may never know what caused the incident.  "We've used the most sophisticated tests that we have available already and basically, the preliminary findings have been negative and usually when you get to this stage, it's very rare that you identify something later."

The ER was closed for several hours Thursday but was reopened later in the evening.