CHP investigators Tuesday were seeking witnesses to Monday’s head-on crash on Highway 12 west of Santa Rosa, which caused one driver to miscarry and critically injured three people.

Officers suspected driver Tristan Taliesin, 41, of Santa Rosa, of being under the influence of drugs and arrested him on a felony DUI charge, CHP Officer Jon Sloat said.

The 4:45 p.m. crash occurred west of Fulton Road, tying up traffic on the two-lane highway and forcing evening commuters to divert to nearby rural roads.

Taliesin’s eastbound Toyota Scion SUV drifted into the opposite lane near Merced Avenue and collided with a Toyota Camry driven by Elizabeth Ehrmann-Subia, 33, of Santa Rosa, Sloat said.

Ehrmann-Subia was 22 weeks pregnant and the impact caused her to miscarry, Sloat said.

The woman and Taliesin both suffered life-threatening injuries. They were taken to Santa Rosa Memorial Hospital along with Ashley Kontos, 27, of Petaluma, who was riding in the Scion. The impact also killed a dog in the Scion.

All three remained in critical condition Tuesday afternoon.

Officers asked anyone with information to call 1‑800-TELL‑CHP or contact officers at the Rohnert Park CHP office at 707‑588‑1400 ext. 238.

You can reach Staff Writer Randi Rossmann at 707‑521-5412 or randi.rossmann@pressdemocrat.com. On Twitter@rossmannreport.