Florida ? NASA is unsure what caused the hydrogen gas leak that prevented space shuttle Discovery from flying, but nonetheless will attempt another launch today.

Shuttle managers are hopeful that repairs at the launch pad have solved the problem.

There’s “a potential risk” that the leak will recur, said Mike Moses, chairman of the mission management team. That would mean another delay for the international space station construction mission, which already is more than a month late.

NASA has until Tuesday to launch Discovery before having to wait for a Russian Soyuz rocket that is set to blast off to the space station March 26.