US Senate candidate Elizabeth Warren has said she was unaware that Harvard Law School had been promoting her purported Native American heritage until she read about it in a newspaper several weeks ago.

But for at least six straight years during Warren’s tenure, Harvard University reported in federally mandated diversity statistics that it had a Native American woman in its senior ranks at the law school. According to both Harvard officials and federal guidelines, those statistics are almost always based on the way employees describe themselves.

In addition, both Harvard’s guidelines and federal regulations for the statistics lay out a specific definition of Native American that Warren does not meet.

The documents suggest for the first time that either Warren or a Harvard administrator classified her repeatedly as Native American in papers prepared for the government in a way that apparently did not adhere to federal diversity guidelines. They raise further questions about Warren’s statements that she was unaware Harvard was promoting her as Native American.

The Warren campaign declined Thursday to answer the Globe’s specific questions about the documents. In a statement, Warren’s spokeswoman, Alethea Harney, said that “over the past month Elizabeth has answered countless questions openly while the people who recruited her have made it clear it was because of her extraordinary skill as a teacher and a groundbreaking scholar.’’

In recent weeks, Warren has repeatedly said that her race was not a factor in her hiring at Harvard or elsewhere, a point that several colleagues and supervisors at the schools have publicly supported. There is nothing in the federally required documents that contradicts those statements.

Warren, who has been dogged with questions about her ancestry since late April, was again grilled by reporters during a campaign stop in Brookline Thursday, but she refused to answer most of the queries, instead trying to shift the focus to Senator Scott Brown’s economic record.

The US Department of Labor requires large employers to collect diversity statistics annually and suggests they be based on employees’ classification of themselves. In cases in which employees do not self-identify, federal regulations allow some administrators to make judgment calls on the correct categories using “employment records or observer identification.’’

The administrator responsible for Harvard Law School’s faculty diversity statistics from 1996 to 2004, the period in question, was Alan Ray, a citizen of the Cherokee Nation who, like Warren, has fair skin, blue eyes, and Oklahoma roots.