NASA told the Washington Post that its review of both SpaceX and Boeing, which have contracts to fly NASA astronauts, will “ensure the companies are meeting NASA’s requirements for workplace safety, including the adherence to a drug-free environment.” The Post reports that multiple NASA officials said the reason was Musk’s public pot smoking.

The safety review will focus on company culture in a series of hundreds of interviews, but there are also technical issues in play.

In October, NASA’s Aerospace Safety Advisory Panel reported [PDF] that “current projected schedules for uncrewed and crewed test flights for both providers have considerable risk and do not appear achievable.” It blamed technical issues for delays and warned that an unrealistic schedule could put crews at risk. It also noted progress on the part of both companies.

SpaceX, which has a $2.6 billion contract to carry NASA astronauts on future missions, issued a statement saying that “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.”

Aerospace giant Boeing, which has a $4.2 billion contract under the same commercial crew program, said in a statement, “As NASA’s trusted partner since the beginning of human spaceflight, we share the same values and are committed to continuing our legacy of trust, openness and mission success.”

Both companies claim they will launch uncrewed flights of their new rockets early next year and crewed flights later in the year.