A major explosion occurred in a residential area in Baltimore, where several people, including children, are trapped, a local firefighters union said on Twitter.
Baltimore Firefighters IAFF Local 734 confirmed the authenticity of its account to CNN by phone without providing additional detail, as first responders -- including members of Local 734 -- were on route the scene.
Three people have been rescued by firefighters, the group said, and the Baltimore Special Rescue Operations Team has begun search and rescue operations.
Baltimore City medical units and Baltimore County Fire Department units also have been called to the scene.
James E. Bentley, the Baltimore City Mayor's spokesman, told CNN he is aware of the reports and was headed into a meeting about the situation.