Officials continue to investigate the cause of a fire at a commercial building in Oshawa on Friday night. It happened at 111 Simcoe St. N. near Colborne St. E. at about 9:15pm. Oshawa's Deputy Fire Chief said the blaze began in a stairwell and is being deemed suspicious. The building contains several businesses including a pharmacy, a legal office, and a methadone clinic. Smoke and water damage to the structure may be as high as $200,000. The fire was extinguished quickly, and there were no injuries as no one was inside at the time.