LOS ANGELES, Nov. 20 (Xinhua) -- The United States space agency NASA has ordered a safety review of SpaceX and Boeing, two companies it has hired to fly astronauts to the International Space Station (ISS), according to U.S. media on Tuesday.

The review was prompted by SpaceX founder and CEO Elon Musk's behavior on a webcast live in September smoking marijuana and sipping whiskey.

NASA described the safety review as a "cultural assessment study" in coordination with SpaceX and Boeing to "ensure the companies are meeting NASA's requirements for workplace safety, including the adherence to a drug-free environment."

"We fully expect our commercial partners to meet all workplace safety requirements in the execution of our missions and the services they provide the American people," NASA said in a statement.

In 2014, SpaceX and Boeing were awarded NASA contracts to build separate capsules to launch astronauts to the space station, with a total value worth up to 6.8 billion U.S. dollars.

SpaceX said in a statement that it took seriously its responsibility to carry NASA astronauts to the ISS and that its engineers had worked side by side with NASA for years to develop its Crew Dragon astronaut capsule.

"There is nothing more important to SpaceX than this endeavor," the company said.

"SpaceX actively promotes workplace safety and we are confident that our comprehensive drug-free workforce and workplace programs exceed all applicable contractual requirements," he said.

"The culture at Boeing ensures the integrity, safety and quality of our products, our people and their work environment," Boeing said in a statement.

NASA Administrator Jim Bridenstine was quoted by media as saying the agency wants to make sure the public has confidence in its human-spaceflight program.

"If I see something that's inappropriate, the key concern to me is what is the culture that led to that inappropriateness and is NASA involved in that," Bridenstine told media.