A high-rise office building in the St. Louis suburb of Clayton is evacuated after what some witnesses described as an explosion.

Witnesses say one person may have been hurt, but that was not immediately confirmed.

The evacuations happened just after 11 a.m. Some people said they heard the explosion, others didn't.

Police dogs were sent to the building to help in the investigation.

Several neighboring buildings were also evacuated as a precaution.

No smoke was visible after the evacuation.

Clayton is the St. Louis County seat and includes many businesses and offices.