An investigation into the explosion in Sun Prairie that killed one firefighter and displaced dozens of people is continuing and close to determining if there was any criminal negligence, Sun Prairie Police Department Lt. Kevin Konopacki said Monday. “We’re getting very close to making that decision,” Konopacki said. Konopacki said the Dane County District Attorney’s office is involved. On July 10 at about 6:30 p.m., We Energies was notified that a third-party contractor hit a gas line. Within a half hour, the explosion occurred. Employees of VC Tech Inc., a contractor working for a Verizon Wireless project in the downtown Sun Prairie area, were on scene prior to the explosion.