FBI investigating suspicious letter containing substance at Minneapolis FAA office

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Emergency responders took four people to the hospital after a Federal Aviation Administration office in Minneapolis received a suspicious letter containing a substance, according to an FBI spokesman.

Police, fire and HAZMAT crews responded to the call at the Flight Standards District Office around 2 p.m.

Investigators with the FBI are evaluating the scene.

It's unclear where this letter came from and to whom it was addressed.

A statement from the FAA says employees in this building oversee aircraft certification, security, pilot licensing and regulatory compliance.

There is no danger to Minneapolis-St. Paul International Airport, which is still operating as normal.