An anonymous reader quotes a report from The Washington Post: The long-running feud between Elon Musk's space company and its fierce competitor United Launch Alliance took a bizarre twist this month when a SpaceX employee visited its facilities at Cape Canaveral, Fla., and asked for access to the roof of one of ULA's buildings. About two weeks earlier, one of SpaceX's rockets blew up on a launchpad while it was awaiting an engine test. As part of the investigation, SpaceX officials had come across something suspicious they wanted to check out, according to three industry officials with knowledge of the episode. SpaceX had still images from video that appeared to show an odd shadow, then a white spot on the roof of a nearby building belonging to ULA, a joint venture between Lockheed Martin and Boeing. The SpaceX representative explained to the ULA officials on site that it was trying to run down all possible leads in what was a cordial, not accusatory, encounter, according to the industry sources, who spoke on the condition of anonymity because of the ongoing investigation. The building, which had been used to refurbish rocket motors known as the SMARF, is just more than a mile away from the launchpad and has a clear line of sight to it. A representative from ULA ultimately denied the SpaceX employee access to the roof and instead called Air Force investigators, who inspected the roof and didn't find anything connecting it to the rocket explosion, the officials said. This week, ten members of Congress sent a four-page letter to several government agencies about the SpaceX explosion, raising the question as to whether or not SpaceX should be leading the investigation. Elon Musk said the investigation into what went wrong is the company's "absolute top priority." He added, "We've eliminated all of the obvious possibilities for what occurred there. So what remains are the less probable answers." SpaceX aims to resume flights in November.