In the federal government's metal shop in Northeast Washington, where parts and pieces are forged and fixed for such places as the White House, the first black supervisor to run the operation came to work one day to find a hangman's noose on his door.

The National Park Service, which runs the shop, said the incident is under investigation, but workers offended by the display said the federal agency is ignoring it.

"They're treating it like it was a joke. I think it was a hate crime," said David B. Melson, the sheet-metal mechanic supervisor at the shop.

Melson said that the shop employee who left the rope is still at work and that since the June incident, no Park Service official has called him to get his side of the story.

"The National Park Service is aware of the incident," said Park Service spokesman Bill Line. "We take incidents of this nature very seriously and deplore these type of incidents. There is an active investigation within the Park Service, and we have to let the internal investigation take its course."

Melson, a shop employee for 10 years and its first black supervisor, said the noose was the most graphic manifestation of racial tension he has felt among the workforce, which is almost evenly split along racial lines.

One of the most obvious strains is in work assignments, Melson said. In most cases, black workers do the heavy lifting at the shop, and white workers are dispatched to the White House to install their handiwork, he said.

On June 2, Melson said, the electricians and metal workers milling about the Brentwood maintenance facility spotted the noose dangling in front of Melson's door.

"I've seen pictures of these things; I've read about them," said Jordan Whitaker, who has worked at the shop for almost eight years. "I would never suspect I would see anything like this on the work site."

Someone called the U.S. Park Police. Then worker John Carrasco tried to grab the rope, and Whitaker tried to stop him, according to a Park Police report.

The two threw punches and shoved each other onto work benches. Carrasco told police that he had placed the noose on a shelf above Melson's door to store it, according to the report.

Both men were put on a day of paid administrative leave. Carrasco, a 67-year-old Mexican American born in Iowa, said he did not mean to offend anyone and had no idea that a hangman's noose is a nefarious symbol. "I didn't know people would be so sensitive," he said. "It was not meant for any harm to anybody. It was an accident. It was a 12-foot-long piece of rope I just threw over my shoulder."

Five shop employees contacted the NAACP, saying the incident was a hate crime that had been ignored by the Park Service. NAACP attorney E. Ned Sloan took the case.

Sloan filed a Equal Employment Opportunity complaint with the Park Service. He is asking that the service fire Carrasco, compensate each offended worker with $250,000 and initiate sensitivity training.