Top executives of Solyndra, the shuttered solar company that received a half-billion dollar federal loan before filing for bankruptcy, refused to answer questions from a congressional subcommittee Friday. They instead invoked their rights against self-incrimination.

Furious Republican lawmakers described the loan as a “taxpayer rip-off” — and they pledged to continue probing whether the firm misled the government and whether the Obama administration rushed its loan approval.

“All the evidence indicates . . . this was a reckless use of taxpayer dollars,” said Rep. Fred Upton (R-Mich.), chairman of the House Energy and Commerce Committee investigating the loan to solar-panel manufacturer Solyndra. “We’re not done.”

Both Republican and Democratic members asked how Solyndra executives could tell them in July that the Silicon Valley firm was doubling sales of its solar panels and then file for bankruptcy Aug. 31.

“You lied to me about the financial health of your company,” Rep. John Sullivan (R-Okla.) said. “I guess a lot can happen in five weeks.”

Solyndra’s two top executives, sitting grimly at the witness table, said they could not provide any answers.

“I have tremendous respect for this subcommittee,” chief executive Brian Harrison said. “As much as I wish to answer the committee’s questions, I have been advised it is the better course” to decline to answer.

Harrison and Bill Stover, chief financial officer for Solyndra, invoked their Fifth Amendment rights at least eight times before Rep. Cliff Stearns (R-Fla.), chairman of the House oversight and investigations subcommittee, excused them.

“I’m disappointed I won’t get answers to those questions,” Rep. Henry A. Waxman (D-Calif.) said.

Upton was particularly frustrated when both men declined to say whether they thought taxpayers deserved information on the use of $535 million in public dollars.

“I don’t know what’s self-incriminating about answering a yes or no question about whether the taxpayers deserve to know what happened to half a billion dollars of their money,” Upton said, shaking his head.

The Justice Department is investigating Solyndra and the loan it received in early 2009. FBI agents raided the company’s Silicon Valley headquarters Sept. 8, a week after the company filed for bankruptcy, laying off 1,100 workers and leaving taxpayers obligated to pay off the loan made through the Federal Financing Bank and guaranteed by the Department of Energy.

Rep. Al Green (D-Tex.) said Solyndra officials were “disingenuous at best” with Congress when they said — on the eve of a committee hearing to subpoena documents — that the company was on track to double sales. He asked if they had been less than honest with the Obama administration and federal officials authorizing their loan.

Several subcommittee members said the White House and DOE were complicit in allowing taxpayers to be victimized in a “Great Train Robbery” by rushing reviewers to approve the Solyndra loan in time for a scheduled event with Vice President Biden.

“The taxpayers deserve answers, and they deserve their money back,” Rep. Tim Murphy (R-Pa.) said.

Upton and Stearns said before the hearing that Harrison and Stover had initially agreed to testify but then reversed course.

The solar-panel manufacturer closed its new seven-acre factory Aug. 31 — just six weeks after Harrison reassured members on Capitol Hill.

Newly released record show company officials alerted the DOE in January that they were out of cash and needed emergency help. The DOE agreed to help Solyndra restructure its loan so it could continue receiving loan installments and delay repayment.

Solyndra was once touted by President Obama as the flagship of his administration’s effort to spur the clean-energy industry.

Also yesterday, with one week left to finish loan deals, the DOE reversed course and told Solar City, which received conditional approval just three weeks ago, that there wasn’t enough time to finish legal documentation. On Sept. 2, the department approved a $275 million loan guarantee for Solar City, a developer, to install solar panels on the rooftops of military housing.

Staff writer Steven Mufson contributed to this report. .