CAPE CANAVERAL, MAY 30 -- The launch of the space shuttle Columbia, scratched Tuesday night because of a mysterious leak of liquid hydrogen fuel, will not occur until at least the middle of next week, NASA officials said today.

Shuttle technicians were still searching for the source of the hydrogen leak that brought the countdown to a sudden stop Tuesday, when hydrogen gas was detected at the rear of the Columbia. The shuttle stood poised on the launch pad, loaded with four research telescopes that have waited since the Challenger explosion in 1986 for their turn in space.

NASA launch director Robert Sieck said today that the most likely leak suspect was a troublesome 17-inch diameter pipe that joins the spacecraft's huge external fuel tank to the shuttle orbiter. Sieck said the fuel leak was from at least a "pinhole source," which spewed hydrogen gas around the rear of the shuttle, setting off sensors. Hydrogen is highly flammable.

Technicians had just begun filling the fuel tank when the sensors went off. NASA officials said the shuttle was never in an unsafe condition.

If the cause of the leak is as simple as a loose seal, Sieck said, Columbia would be ready for a launch by the middle of next week at the earliest. If the problem is more serious, Columbia will have to be rolled back from the launch pad to the huge hangar nearby to undergo more extensive repairs.

Sieck said that technicians would be searching for the leak throughout the night. They have been delayed in their investigation because they first had to wait for the hydrogen in the tanks to boil off.

Columbia was scheduled to carry seven men and four research telescopes into orbit, where they would peer into the heavens, using special detectors to see ultraviolet light and X-rays. Columbia's flight, already delayed for several weeks because of problems with the cooling system, now threatens to delay subsequent launches.