COTTAGE GROVE, MINN. — The Opus Group will build a 35,600-square-foot expansion for North Star Sheets at Southeast Industrial Park in Cottage Grove, about 10 miles south of St. Paul. North Star Sheets, a producer of corrugated paper products for manufacturing needs, currently occupies a 168,000-square-foot building on 16 acres. The company will use the expansion to increase capacity and add another rail spur to enhance its rail service infrastructure. Opus will serve as developer, design-builder, architect and structural engineer. Hillcrest Development LLLP owns Southeast Industrial Park. Eric Rossbach and Andy Heieie of Colliers International are the leasing agents for the property.