PORTLAND, Ore. (AP) — The names of two men killed in a fire at a three-building apartment complex on Sunday in Northeast Portland have been released.

Robert William Gremillion, 31 and Seth Robert Thompson, 31, died when the blaze swept through Heidi Manor in the early morning hours of July 4, KOIN-TV reported.

Six other people were hurt including a 25-year-old woman who remains hospitalized with critical injuries, police and fire officials said.

Fire crews secured the structure on Tuesday, making it possible for investigators to go inside on Wednesday. An official cause of the fire has yet to be determined.

Residents, many of whom jumped from rear bedroom windows or balconies, told The Oregonian/OregonLive they saw flames initially in a dumpster that was placed in the carport under the apartments. Several also had heard fireworks coming from the front of the complex prior to seeing flames.

Fire investigators said they believe that there are people with critical information who have not come forward. They ask anyone with information to contact Detective Meredith Hopper at Meredith.hopper@portlandoregon.gov.