By Phil Matier

OAKLAND (CBS SF) — Oakland police say they are investigating reports that a noose was found placed on a city Public Works truck used by African American employees, and the workers union says they have no doubt it the move was rooted in racism.

The noose was reported Tuesday after 5 p.m. at the City Corporation Yard on Edgewater Drive, according to police spokeswoman Johnna Watson.

READ MORE: Contractor Who Bribed San Francisco Public Works Director Sentenced to 2 Years in Prison

One employee wasn’t surprised by the discovery.

“There’s been some issues going on there for quite some time now,” Service Employee Union worker Al Marshall said.

Asked if racial tension was one of the issues, Marshall answered “I can say yes.”

Oakland Mayor Jean Quan told KPIX 5 she was aware of issues in the department.

READ MORE: Warnings About San Francisco Millennium Tower Repair Plans Raised Before Work Began

“There’s the general stuff around who gets promoted, who doesn’t get promoted – that kind of thing, but nothing that has been a racial issue,” Quan said.

Watson said the department has not investigated any similar reports in recent years.

“The Oakland Police Department takes this incident very seriously,” Watson said.

Speaking to the media Wednesday, interim City Administrator Henry Gardner said, “I take this very seriously.”

MORE NEWS: Video Released of Suspect In Assault Pro-Recall Supporter in San Rafael

“There is an investigation underway, it will be vigorous, it will be thorough, it will be complete and there will be severe consequences if we can identify who put it there,” Gardner said.