(Seattle, WA) -- A fifth company is now under investigation in connection to Saturday's deadly crane collapse that killed a Portland-area construction worker in downtown Seattle. The Washington State Department of Labor and Industries announced yesterday they're expanding their probe into the companies involved in dismantling the crane before it collapsed and crashed onto a busy street, killing four people and injuring another four. Department spokesman Tim Church tells CNN the investigation could take up to six months to complete. Ironworkers Local 29 member Travis Corbet of Oregon City was one of two crane operators killed in the crash. Local 29 business manager Joe Bowers says he had just recently married.