LONGMONT, Colo. (CBS4) – Investigators had to don protective suits as they are trying to determine what killed a 6-year-old girl in Longmont Monday morning.

The investigation began at approximately 9 a.m. when the girl, identified as Lluvia Espinoza Morales, was taken to the hospital. She was pronounced dead at the hospital, but there were no signs of foul play.

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Police started going down the list of what could have killed the girl. One thought is that she had influenza. Investigators consulted with the Centers for Disease Control and Prevention on how to go in to the girl’s home.

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Crews in hazmat suits, using all the precautions, entered the girl’s home. Some were also washed down when they were done.

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Investigators still don’t have an idea of what killed Morales. It could be flu, but they said it could be something else. The final determination is going to be made by the coroner, but that could take several weeks.