The crash happened along Martin Luther King Way S. at the S. Brandon St. intersection around 3:30 p.m., Seattle Fire Department officials said.
A 6-year-old was taken to Seattle Children's Hospital in stable condition while four others were being taken to Harborview Medical Center with serious-to-minor injuries, Seattle fire and police officials said. A sixth patient was treated at the scene. Passengers say one victim was on the train and hit his head against one of the train's windows, smashing it.
Sound Transit officials say it appear the driver of the van was attempting to make a left-hand turn onto Brandon Street against the signal when it crashed into the southbound train.
Link service was disrupted between Mt. Baker and Othello stations and Sound Transit was busing passengers to bridge the closure. Lane closures near the crash scene also snarled vehicle traffic.