Two people were injured in a chain-reaction collision Sunday in Petaluma caused by a 19-year-old Petaluma woman later arrested on suspicion of drunken driving, police said.

The crash was one of two drunken-driving arrests Petaluma police made before lunch over the weekend, Lt. Ken Savano said.

Police suspect Kaitlyn Keene, 19, of Petaluma was drunk when she rear-ended the vehicle in front of her on Petaluma Boulevard North near Western Avenue at about 9:50 a.m. Sunday, Savano said. She crashed into a Honda CRV, injuring driver Donna Savarese, 53, of Petaluma and causing the Honda to crash into a Ford Explorer, Savano said. A passenger in the Ford, Connie Floyd, 69, of Petaluma also was injured. Both Savarese and Floyd suffered minor injuries. Savarese was taken to a hospital, police said.

The second arrest occurred at 10:30 a.m. Saturday after residents on Mauro Pietro Drive in east Petaluma called police to report a woman was passed out behind the wheel of a 2002 Suzuki Aero in the roadway, Savano said.

A preliminary test of Daisy Austin, 27, of Santa Rosa found her blood-alcohol level to be 0.3 percent, nearly four times the legal limit, Savano said. She was booked into the Sonoma County Jail on suspicion of drunken driving, he said.