Eight men were tragically killed in a two-vehicle head-on crash in Madera, California on Friday Feb. 23, authorities say.

In total, there were nine men involved in the crash, but one passenger survived, the California Highway Patrol reports.

At approximately 6:15 a.m. the driver of a black Chevrolet pickup truck crashed into a GMC van carrying eight people after swerving in and out of the two-lane highway in Madera, about 25 miles northwest Fresno, police said. One passenger, seated in the rear of the van, survived the crash and was taken to a local hospital. He is expected to recover from his injuries.

The AP is reporting that only two people in the van were wearing seatbelts. "If they had been wearing their seatbelts, the rear passengers would have probably survived," CHP Officer Javier Ruvalcaba said.

The men in the van were farmworkers headed to work at the vineyard where they were employed. The vineyard was about five miles away from where the crash happened, the Associated Press reports.

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The wife of one of the farmers witnessed the tragedy, police investigating

The wife of one of the farmers was in another van following closely behind them. CHP says she witnessed the crash, a report from Your Central Valley said.

Police are investigating what led up to the crash and if alcohol was involved.

“At this point, we don’t know whether alcohol or drugs played a factor,” Ruvalcaba said.

Contributing: The Associated Press