A Gonzales woman died Friday from injuries sustained in an early morning crash on Interstate 10 that killed the only other person in the SUV, State Police said.

Karen Matherne, 50, died sometime after the Cadillac SRX she was riding in broke through a guardrail, crashed into Bayou Manchac and sank, said Trooper 1st Class Jared Sandifer, a State Police spokesman.

The driver of the SUV, Armand M. Marchand IV, died at Our Lady of the Lake Regional Medical Center earlier in the day.

Sandifer said he wasn’t sure if Marchand or Matherne died from injuries suffered in the crash or if either of them drowned. He added that a doctor would have to determine the causes of their deaths.

The crash happened about 12:30 a.m. May 23 on I-10 east of La. 42, also known as Highland Road. Troopers believe excessive speed was a factor in the crash, Sandifer said.

Marchand was wearing a seat belt during the crash, and investigators did not know whether Matherne was restrained in the crash, Sandifer said.

Both Marchand and Matherne were pulled from the mostly submerged wreckage by firefighters with the St. George Fire Department, Sandifer said.

Both were then taken to the hospital. However, police did not initially release the fact that Matherne was injured in the crash.

Troopers submitted toxicology samples to lab analysts in an effort to determine whether impairment was a factor in the crash, Sandifer said.

A total of four people, including Marchand and Matherne, have died in three crashes in East Baton Rouge Parish since Friday, authorities reported.