Elon Musk, the founder of SpaceX (left) and the Sept. 1, 2016, explosion of a Falcon 9 rocket (right) in Cape Canaveral, Fla. Max Whitaker/Getty Images; USLaunchReport.com; Business Insider

On September 1, a SpaceX rocket burst into flames during a routine launchpad test, destroying a $200 million satellite that Facebook planned to lease.

An ongoing investigation into the fireball, which occurred at Space Launch Complex 40 (SLC-40) in Cape Canaveral, Fla., has narrowed the blast's origin to a breach in a helium tank.

However, SpaceX has said the exact cause remains elusive.

According to journalist Christian Davenport, writing in the Washington Post, SpaceX investigators have considered "something suspicious" they saw on the roof of its biggest rival: United Launch Alliance (ULA), a company that's jointly owned by aerospace giants Boeing and Lockheed Martin.

The unsaid implication and speculation here, an industry source recently suggested to Business Insider, is this: It may be possible that someone could have gotten access to the roof of ULA's building, fired a bullet or other projectile from more than 5,300 feet in the distance, and somehow struck the Falcon 9 rocket's upper stage.

Davenport wrote that, based on conversations with three industry officials, SpaceX (reportedly) "had still images from video that appeared to show an odd shadow, then a white spot on the roof of a nearby building leased by ULA ... The building ... known as the SMARF [Solid Motor Assembly and Readiness Facility], is just more than a mile away from the launchpad and has a clear line of sight to it."

Davenport notes the SpaceX investigation team was simply pursuing all possible leads, and a spokesperson told Business Insider as much in an email. The Washington Post article goes on to say that, while the interaction between SpaceX and ULA officials was "cordial," the US Air Force (USAF) ultimately went up to the SMARF roof to check things out.

But does anyone in the industry believe sabotage is a real possibility?

We spoke to a ULA worker in Cape Canaveral on condition of anonymity (due to security concerns) who has followed a lot of gossip within the company. The worker told Business Insider that ULA staff seem to be treating the notion as "pretty much a joke out here," though of course this is just one worker's impression.

"What happened is SpaceX wanted access to [the SMARF] roof, probably just to tie up a loose end," the worker said. "Instead the Air Force went up, found nothing."

The ULA's SMARF building is more than a mile away from the site of the SpaceX launchpad fire. Google Maps/Business Insider Despite its extreme unlikelihood, the worker said, the notion of sabotage has made for "fascinating" gossip among ULA staff. "Could someone sneak a rifle up there, could they disguise the noise, could they hit the rocket, would it do anything if they did hit it?"

Still, the source underscored the mundane nature of the theory's alleged origin — and its improbability.

"SpaceX has a fault analysis tree, and [sabotage] is a branch of it that needs tying up," the worker clarified, further noting that, based on his impression: "I don't see them or anyone here giving it any credence."

That's the word on the street at the ULA office, according to our source, and ULA itself mostly confirmed his take, in broad strokes.

When provided with some of these unattributed comments, a ULA representative told Business Insider in an email that the company "cooperated with the Air Force's 45th Space Wing [of the USAF], and nothing associated with the SpaceX accident was found."

Given some of the same comments, a SpaceX spokesperson told Business Insider in an email:

"The Accident Investigation Team has an obligation to consider all possible causes of the anomaly, and we aren't commenting on any specific potential cause until the investigation is complete. ... We have sought all available data to support the investigation in a timely manner following the anomaly, as expected for any responsible investigation."

In the meantime, lawmakers on Capitol Hill are sparring over the independence and rigor of SpaceX's internally led probe, which the Federal Aviation Administration (FAA) approved after SpaceX submitted its investigation plan.

In one camp are 10 House Republicans who recently called for the FAA, NASA, and USAF to take over the investigation, despite current approval, oversight, and involvement by federal agencies. Those congressmen, as Business Insider recently reported, received campaign donations from ULA, Boeing, and Lockheed Martin, and some have local interests in supporting ULA.

But a larger, bipartisan group of lawmakers — half of whom SpaceX has donated to in the most recent election cycle, and some of whom represent districts in which SpaceX conducts its business — have rebutted the call for a full government takeover of SpaceX's probe.

"Accidents are unfortunate events, and accident investigations should not be politicized. We encourage you to reject calls for your organizations to abandon established, well considered, and long standing procedures," the latter group of lawmakers wrote.