Echo 33, engine four, responding to mile marker 137 on Interstate 25 for a possible vehicle rollover. Units discuss location, confirm southbound near an underpass. Multiple engines and dispatch coordination heard. Upon arrival at the scene near the underpass, crews report no vehicle present. They continue search along nearby roads. Discussion follows of a semi truck seen earlier, but nothing found. Later, responders assess steam near an ice rink north of 137 as likely mistaken for smoke from an accident. Conclude no crash on the interstate.