Some serious shadiness going on here.

(ABC News) — House investigators said they have uncovered evidence that White House officials became personally involved in an Energy Department review of a hot-button $535 million loan guarantee to the now-failed California solar company Solyndra.

The allegation surfaced in a letter House Energy Committee Chairman Fred Upton (R-Mich.) sent to the White House Thursday night, saying he planned to accelerate efforts to understand an investment deal that may have left taxpayers out half a billion dollars.

“We have learned from our investigation that White House officials monitored Solyndra’s application and communicated with [Department of Energy] and Office of Management and Budget officials during the course of their review,” the letter says.

Thursday’s letter, which calls on the White House to turn over correspondence between administration officials, Solyndra and its investors, presents the most pointed suggestion that the White House had direct involvement in the financing.

“How did this company, without maybe the best economic plan, all of a sudden get to the head of the line?” Upton told ABC News in an interview this week. “We want to know who made this decision . . . and we’re not going to stop until we get those answers.”