Howard County police are investigating a weekend accident on Route 97 that sent two Carroll County teen-agers to a hospital with life-threatening injuries.

A Ford Explorer driven by Joanna Nasios, 22, of Brookeville, Montgomery County, was traveling south on Route 97 near Cattail Creek Road about 3:10 a.m. Saturday when it crossed the double yellow line and hit a Chevrolet Cavalier, police said.

The driver of the Cavalier, Kaleigh Rinaldi, 16, of Marriottsville, and passenger Tressa Mielke, 18, of Sykesville were flown to Maryland Shock Trauma Center, police said.

Rinaldi was in critical condition and Mielke in serious condition, a hospital spokeswoman said yesterday. Nasios was treated at Montgomery General Hospital and released.

No charges had been filed.