Tacoma fire investigators say it was lithium ion batteries inside an electronic that caused a fire at Simon Metals early Monday morning. Investigators say spontaneous combustion of the batteries sparked the fire. The blaze erupted around 2 a.m. Monday in the bottom of a scrap pile and it took firefighters more than six hours to contain the flames. Thick smoke billowed into the sky but it was the smell that got people's attention. The blanket of smoke eventually disappeared with the wind but concerns lingered over air quality. “I wouldn’t be breathing that stuff,” Erik Forseth said. Forseth was miles away from the Simon Metals fire in a nearby neighborhood on Monday but he and others say they could see and smell it. “It looked like thick fog but it wasn't -- it was smoke, nasty smell,” said one man.