A 21-year-old Ukiah woman who fell into the path of a passing big-rig suffered major injuries Thursday afternoon when her leg was run over by the rear dual wheels of the semi trailer, the CHP said.

Madeline Anderson was riding her bicycle eastbound on Highway 253 just outside of Ukiah with her 13-year-old brother, who was not injured, the CHP said.

But Anderson was flown to Santa Rosa Memorial Hospital with major injuries from the 4:22 p.m. accident, authorities said. Her condition was not available Friday.

Authorities said the pair was riding single file, approaching a dirt turnout near Stipp Lane, when a big-rig driven by Ukiah resident Barbara Jones, 52, shifted left and straddled the double yellow center lines to pass the bicyclists.

Anderson's brother was riding in front and thought his sister yelled for him to stop, so he did, the CHP said.

But Anderson wasn't able to brake fast enough and swerved to his left to avoid a collision. Instead she came up against the semi trailer, lost her balance and fell into its path, authorities said.

The CHP said Jones was traveling about 25 mph.

Anderson was not wearing a helmet, the CHP said. The scope of her injuries was unclear.