Federal labor agents are investigating the death of a 55-year-old vineyard worker who was killed in a vehicle accident along Guerneville Road while commuting to work.

The Aug. 3 crash involved five employees of Madera-based Mid Valley Labor Services, Inc. Passenger Manuel Acosta Montano was killed when the car flipped. The driver, 19-year-old Laureno Terrazas fled and was later arrested and charged in connection with the crash, including driving without a license.

The crash sparked an inquiry by investigators with the U.S. Department of Labor into whether Mid Valley followed federal laws that regulate how laborers get to work, said Susana Rincon, district director of the department's wage and hour division in San Francisco.

"Because it involves farm workers we decided to go ahead and see if there were any violations with the law," Rincon said.

"It's a fatality, it's considered a priority for us," she said.

If the labor contractor was involved in the group's carpooling arrangements, the company could be held liable for the crash, Rincon said.

Ben Mascarenas, Mid Valley president, said the five men were traveling in an independent carpool not affiliated with his company.

But labor agents said the company could still be liable if they find the men's carpool fell under protections set by the Migrant and Seasonal Agricultural Worker Protection Act, Rincon said.

"Is the driver being paid to transport them? Is he charging a fee to transport employees? Is he being paid extra or getting an incentive to drive employees to one field to another?" Rincon said.

Terrazas picked up four fellow workers from a Santa Rosa neighborhood that early August morning in a green Chevrolet Astro van, CHP officials said.

Mascarenas said they were heading to work at Kendall-Jackson's Seascape vineyard near Occidental.

Terrazas was driving the group down Guerneville Road at about 5:10 a.m. when the car drifted into a gravel shoulder just west of Olivet Road, CHP officials said. The van jumped the ridge of a driveway, struck a pine tree and flipped.

Acosta Montano, who wasn't wearing a seat belt, was ejected and the van landed on its side on top of him, the CHP said.

Terrazas allegedly ran into a nearby vineyard after the crash and disappeared. Officers later found and arrested him at his girlfriend's Santa Rosa apartment.

He was charged Aug. 5 with hit and run with injury or death, vehicular manslaughter with gross negligence and driving without a license. He was being held without bail.

The crash is the second inquiry into the company in the past year, labor investigators said.

After a 2009 site visit, labor investigators early this year found Mid Valley was responsible for fees its workers were paying to a crew boss at a San Joaquin valley site who drove them to and from work, Mascarenas said.

The determination was "that crew boss was, for all intents and purposes, representing our company," Mascarenas said.

Mid Valley paid 22 workers about $37 each as a result, he said.