Nasa has said it is launching a probe into workplace safety at Space X, prompted by the company's founder Elon Musk smoking marijuana during an interview.
The review into Space X as a commercial partner of Nasa, which will also include an investigation at Boeing, comes as both companies prepare to fly astronauts up to the International Space Station.
Nasa will conduct a "cultural assessment study" of Space X and Boeing as part of the probe, which is to include "the adherence to a drug-free environment" ahead of test flights scheduled in the coming months.
Expected to take several months, the Washington Post reported Nasa was inspired to carry out the probe after Musk smoked marijuana while appearing on the Joe Rogan podcast in September.
Though recreational usage of the drug is legal in California where the podcast was recorded, it remains forbidden across many US states and by both Nasa and the US military.
"We fully expect our commercial partners to meet all workplace safety requirements in the execution of our missions," the space agency said in a statement.
Boeing said in an emailed statement to Reuters that it was committed to mission success as a partner of Nasa, while ensuring the integrity, safety and quality of its products, its people and their work environment.
A Space X spokesperson said: "We take seriously the responsibility that Nasa has entrusted in us to safely and reliably carry American astronauts to and from the International Space Station."
"We are confident that our comprehensive drug-free workforce and workplace programmes exceed all applicable contractual requirements."