GOTEBORG, Sweden (AP) _ The fire that killed 63 young people in a second-floor dance hall began in the emergency exit stairway but what caused the fire to start is still unknown, investigators said Wednesday.

The fire just before midnight on Oct. 29 blocked one of two exits from the hall where teen-agers had organized a dance, forcing the panicked crowd to try to flee down the remaining stairway or jump out of windows.

Investigators said they would question workers who had redone some of the building's electrical wiring in recent years, including wiring in the emergency exit.

The fire's quick spread has led to speculation that it may have been arson.