US space agency NASA said it would investigate reports that astronauts on at least two occasions violated rules against drinking before flying.
An independent panel investigating the health and psychological care of astronauts reported on Friday that it had been told of two incidents in which concerns about crew members drinking were raised to flight surgeons in the hours immediately before launch.
NASA officials at press conference in Washington said they could not provide details of when the incidents occurred, but said they would conduct a more thorough review.
Air Force Colonel Richard Bachmann, the doctor who led the review, said the panel was told of two incidents one involving a shuttle and a T-38 training vehicle and the other involving a Russian Soyuz craft in which personnel said they felt their concerns about drinking were disregarded.
Bachmann said the alleged incidents could be illustrative of feelings within the astronaut corps that such concerns would be ignored.
He said he could not provide details about specific missions or astronauts that may have been involved.
He said the panel had the sense that such concerns were "not unique to the shuttle, not unique to the T-38, not unique to the space station".
NASA Deputy Administrator Shana Dale said the US space agency would review its alcohol policy and investigate the alleged incidents.
Officials also said they would clarify a policy that prohibits astronauts from drinking in the 12 hours before a flight.
Dale said NASA wants to ensure that there is "an open culture here and people are empowered to raise any safety concerns".
The review of NASA's health policies was begun after astronaut Lisa Nowak was arrested for allegedly stalking and threatening another woman she believed to be a romantic rival for the affections of an astronaut.