Oregon’s investigation into discrimination at a Portland truck-making plant has broadened after four more workers filed civil rights complaints against Daimler Trucks North America, AP reports.

The German automotive giant now faces nine complaints, which include allegations of racial discrimination against African-American employees and other minorities. Daimler Trucks’ corporate headquarters and Western Star factory lines are also being investigated by the state Bureau of Labor and Industries.

According to the employees who prompted the Oct. 1 launch of the investigation, they faced ongoing unfair treatment based on race, nationality and age from co-workers or supervisors and neglect from management regarding the incidents. Threats of physical violence and the repeated use of the N-word, "boy," "buckwheat," "Toby" and other racial slurs were also reported.

One Black Daimler worker alleged that a co-worker threatened him with a noose last fall and no "appropriate corrective action" was taken by management.

"He told me he was going to hogtie me to the back of his truck, and when he was done with me I would be 100 pounds lighter," the employee said.

Daimler Trucks spokesman David Giroux released a statement on Wednesday, saying that the company is cooperating with the state investigation and has hired its own investigator to look into the claims. The company has a zero-tolerance policy regarding discrimination or harassment on any basis and is committed to diversity and inclusion, he added.

"Our investigators will see whether there's evidence of a pattern of oppression, of assaults, of racial epithets, and whether the long history of abusive conduct is still affecting the workplace today. And I believe it is,” Oregon’s labor commissioner Brad Avakian told AP.

AP reports that at least 27 civil rights complaints have been filed against the company from 2002 to 2013.

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(Photo: REUTERS /BABU /LANDOV)