WASHINGTON — After finding no evidence of astronauts drinking before launching into space, NASA said Wednesday it is considering limited alcohol testing of its employees, including astronauts.

An internal investigation recommended alcohol testing while at the same time clearing astronauts of much-publicized drinking allegations. In response, NASA Administrator Michael Griffin said he would come up with a policy for testing after a mishap or when there are suspicions of substance abuse. It would, he said, be further validation of a sober space agency.

The review released Wednesday could not verify two drinking allegations described by an independent panel last month, and Griffin said they just didn’t happen. The report did acknowledge the availability of alcohol in crew quarters, noting that non-flying astronauts made booze-buying runs for their quarantined colleagues.

The 45-page report by NASA safety chief Bryan O’Connor, a former astronaut and shuttle accident investigator, was initiated after the July report on astronaut health by eight medical experts.

“I was unable to verify any case in which an astronaut spaceflight crewmember was impaired on launch day” or any case where a manager disregarded warnings from another NASA employee that an astronaut not fly, said O’Connor’s report.

However, O’Connor said NASA doctors should play a stronger “oversight” role on launch day, accompanying astronauts as they suit up for launch. O’Connor also recommended that excessive drinking be added to NASA’s list of risky activities forbidden for astronauts in the year before launch, along with motorcycle racing, parachuting and firefighting.

A 1991 law directs NASA to come up with a policy for alcohol testing of employees as recommended by O’Connor, but it never has done so before, Griffin said at a news conference. He said the agency will now start the long process of coming up with a testing policy.

“The issue is just how far we go,” he said after the conference.