Firefighters engaged a massive 5-Alarm fire at an unknown commercial building in Riverside County Monday afternoon. The fire was first reported at around 1:30 p.m. 22000 block of Opportunity Way where it quickly grew to engulf more than 10 acres of cardboard, outside storage area and other materials by 3 p.m. According to Cal Fire/Riverside County Fire Department, the flames were approximately 15 feet to 25 feet high. One firefighter was rushed to a nearby hospital for treatment on non-life-threatening injuries suffered during the incident. A hard road closure was issued on Opportunity Way between Van Buren Boulevard and Meridian Parkway, according to firefighters.