LARKSPUR, Colo. (KDVR) — Update: 2:40 p.m. 4/27: I-25 southbound has been reopened between Exit 181 and Exit 174.

Original Story: The Colorado Department of Transportation said fire activity is shutting down I-25 southbound in the Larkspur area Wednesday afternoon.

According to Colorado State Patrol Master Trooper Gary Cutler, this is a hazmat situation. Cutler said Castle Rock hazmat is on scene.

A density gauge fell off a vehicle and broke, exposing radioactive material, according to CSP.

CDOT tweeted about the closure at Exit 174 just before noon. The closure extends to Exit 163.

There is no estimated timetable for the road to reopen. You can check for the latest traffic patterns here.

This is a developing news story. Check back here for new details.