The jet bridge failure is "under investigation" according to BWI.
Multiple emergency services personnel responded to the scene, transporting at least six people to area hospitals with non-life-threatening injuries.
It is not yet clear whether the six who were injured were passengers, first responders or airline employees. It is owned by BWI Marshall.
"There was a partial failure of the equipment the jet bridge at gate E-10".
The plane arrived from Punta Cana, Domincan Republic, and at around 8 p.m. requested paramedics to help with a medical situation involving a passenger on the flight, Southwest Airlines said in a statement.
An investigation into the incident is underway while the jet bridge has been closed temporarily. The aircraft has been moved from the gate and there is no further impact to operations, it said.