Madison crews are responding to a report of a hazardous material incident at a west Madison building Thursday afternoon, an official says. Madison Fire Department spokeswoman Cynthia Schuster said firefighters and the hazmat team were sent to 601 Science Drive at 1:09 p.m. for a report of two chemicals that had combined in the lab, causing a toxic mixture. The spill took place at MilliporeSigma, one of the private company tenants at the University Science Center. Responders were told that 200 milliliters of nitric acid were combined with one liter of an unknown chemical inside a container at 601 Science Drive.