MINNEAPOLIS (AP) — Fire officials say they haven’t been able to determine the cause of a high-rise apartment fire that killed five people last week in Minneapolis.

The Minneapolis Fire Department says Monday that the investigation into Wednesday’s fire is completed. Officials found the blaze was accidental, but they weren’t able to pinpoint the exact cause. Its origin was a bedroom wall in a unit on the 14th floor.

The apartment building is 50 years old and was not required to have sprinklers due to its age.

The complex that includes this building was scheduled for a routine inspection by the U.S. Department of Housing and Urban Development on Monday. But HUD said that inspection is being rescheduled.

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