By Roberta Rampton

WASHINGTON (Reuters) - A top Republican congressional watchdog wants the Energy Department to turn over documents and emails about $4.7 billion in loan guarantees for four solar projects approved right before a Sept 30 deadline.

The last-minute approvals of the projects raise fears that "the evaluation of loan guarantees may have been rushed in order to meet a deadline," said Darrell Issa, chairman of the House Oversight Committee, in a letter to Energy Secretary Steven Chu.

Issa and other Republicans in the House of Representatives have pushed to highlight concerns about a loan guarantee to Solyndra, a failed solar panel manufacturer that has filed for bankruptcy and is being investigated by the FBI.

Solyndra was the first company to receive an Energy Department loan guarantee, worth $535 million, in 2009. The Solyndra investigation has been politically embarrassing for the Obama administration, which had made clean energy job creation a key plank in its energy policy.

Funding for the program expired on Sept 30, and on that day, the department approved loan guarantees to First Solar Inc for two solar power plants and SunPower Corp for another plant.

The projects were different than Solyndra. While Solyndra's loan went toward building a factory, the three power plants approved Sept 30 had a fixed revenue stream from contracts for the electricity produced by the plants.

After the Energy Department approved the loan guarantees, the plants were bought by some of the largest utilities in the nation.

The committee wants to know whether the sale of the projects to the utilities was a condition for approval of the loans.

Exelon bought First Solar's Antelope Valley project, while NextEra Energy and GE's Energy Financial Services bought First Solar's Desert Sunlight plant.

NRG Energy bought SunPower's California Valley project.

The fourth loan guarantee was for a project owned by Prologis to install solar panels on industrial buildings, which was also backed by NRG.

Issa asked for emails between the Energy Department and all the companies involved, as well as emails between the Energy Department and White House concerning the projects.

The panel also asked a series of questions about the technology used by First Solar, and asked why the Energy Department failed to finalize a guarantee for First Solar's Topaz plant.

The House Energy and Commerce Committee has been leading the probe of Solyndra and the loan guarantees, and is slated to hold another hearing on the issue on Friday.

(Editing by Cynthia Osterman)