The State Department said Tuesday it has no record of Hillary Clinton signing a key form stating she turned over all official documents upon leaving the department -- a form that was the subject of intense speculation since the issue could determine whether she broke the law. 

That document is known as a "separation" form, which officials are supposed to sign upon leaving the department. It certifies that the person who signs it has turned over all "classified or administratively controlled" materials, as well as all "unclassified documents and papers" relating to official government business. 

Given that Clinton exclusively used personal email while secretary of state and didn't turn over official records until late last year, a former Justice Department official said last week that if Clinton signed that form, she probably gave a false statement and broke the law. 

But on Tuesday, State Department spokeswoman Jen Psaki told reporters they are "fairly certain she did not" sign it. 

"We have reviewed Secretary Clinton's official personnel file and administrative files and do not have any record of her signing the OF109 [form]," Psaki said. 

This admission comes after the department for days was unable to answer questions about whether Clinton signed the form. 

It also raises questions about whether Clinton, by not signing it, at least violated department policy. 

Psaki claimed Clinton did not violate any policy. Further, she said Tuesday that neither of Clinton's two immediate predecessors, Colin Powell and Condoleezza Rice, signed such a statement either. 

She also said that different bureaus within the department had different rules relating to such statements that had the effect of making their completion optional by some employees. 

Shannen Coffin, a senior lawyer under the George W. Bush administration, first cited the form OF109 in questioning whether Clinton committed a violation by exclusively using personal email as secretary of state, and then not turning over those emails deemed work-related until after leaving the department. 

If she indeed signed the document, he told Fox News last week, "there's no question [she broke the law]."

And if Clinton did not sign that document, he added, "why not?" 

The Associated Press contributed to this report.