One man was killed and another critically injured Sunday in wrong-way, head-on collision on southbound Interstate 5, according to the San Diego Fire-Rescue Department.

The crash happened around 4 p.m. on I-5 at the Civic Center/Front Street exit near the transition to state Route 163, Battalion Chief Rick Ballard said.

A black Nissan Versa crashed head-on into a white Volkswagen minivan, according to the California Highway Patrol.

The Nissan driver was coming from SR-163 the wrong way and crossed all lanes of I-5 before hitting the minivan and slamming into the center divider, CHP Sgt. Ray Scheidnes said.

Both drivers were trapped and had to be extricated, Battalion Chief Dan Eddy said.

CHP investigators are still looking for the cause of the crash. NBC 7's Erika Cervantes has more.

The Nissan driver, identified only as a 44-year-old man from Lebanon, Maine, was pronounced dead at the scene.

The other driver, a 67-year-old San Diego man, was critically injured and transported to UCSD Medical Center, he said.

"You know, we see sometimes confused drivers, people driving under the influence," Scheidnes said. "Unfortunately, when drivers are confused it could be because we have elderly drivers or inexperienced drivers, who lose their bearing and make an honest mistake."

Alcohol was not believed to be a factor in the fatal crash, Scheidnes said.

The minivan driver was unresponsive at the time, Eddy said.

"He had apparently some complaining of pain to his chest and to his right leg," said Scheidnes.

A SigAlert was issued around 4:15 p.m. because the left three lanes of I-5 were blocked. All lanes reopened around 6:45 p.m.

The cause of the crash was under investigation.