3-year-old child dies aboard asylum-seeker bus heading to Chicago area from Texas: sources

CHICAGO (WLS) -- An investigation is underway into the death of 3-year-old child who was aboard a bus of asylum-seekers.

The Illinois Department of Public Health confirmed it happened on Thursday while the bus was heading to the Chicago area.

A source familiar with the investigation and a Brownsville city spokesperson both told ABC News that the bus originated in Brownsville, Texas.

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"IDPH is working with local health officials, state police, and federal authorities to the fullest extent possible to get answers in this tragic situation," IDPH said in a statement.

There's no word yet on how the child died. Officials did not immediately provide further information.

ABC News contributed to this report.