House Republicans' lead Solyndra investigator continued to keep the witness list for a highly anticipated hearing Friday under his hat last night, but he did confirm that he does expect an official from the Department of Treasury to testify.

House Energy and Commerce investigations subcommittee Chairman Cliff Stearns (R-Fla.) said in an interview that he had invited an official from Treasury to appear before his committee based on a series of emails that had been uncovered Friday as part of his ongoing investigation.

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Solyndra, a solar manufacturer that was given a $535 million loan guarantee and touted by the White House as a model for the clean energy economy, has filed for bankruptcy. E&E examines how it got there and what it means. Click here to read the report.

A key question Republicans have been hounding Obama administration officials on is whether the Department of Energy had the legal authority to restructure Solyndra's loan earlier this year under terms that subordinated the government's more than half-billion-dollar investment to new funding from private investors.

It turns out that the Treasury Department's chief financial officer for the Federal Financing Bank, Gary Burner, and Assistant Treasury Secretary Mary Miller both expressed concerns about that exact issue at different points this year in emails to agency officials. Miller questioned DOE's legal justification as recently as August (E&E Daily, Oct. 11).

"The obvious question is what did you base your [concerns] on?" Stearns said of his expected line of questioning for the Treasury Department official. "What legal brief? And what legal brief did DOE use [to justify their actions]? And do you think it's against the law?"

Stearns did not rule out having other witnesses from DOE or another agency testify Friday.

"We're still working on it," he said.