Spacewalking astronauts encountered leaking ammonia and minor glove damage while performing plumbing work outside the International Space Station on Friday, but NASA said neither issue posed an immediate threat.

NASA astronaut Kjell Lindgren reported intermittent flakes of toxic ammonia while making connections in a cooling line. He assured Mission Control it appeared to be just a small leak.

Mission Control stressed that the astronauts were in no danger.

Lindgren and NASA's one-year spaceman, Scott Kelly, the station's commander, were about two hours into their planned 6½-hour spacewalk when the ammonia flakes spewed out. As long as the men were outside, any potential suit contamination would pose no concern. But before going back in, they would need to make certain that any traces of ammonia had been removed by the sun.

In the past, several spacewalkers have been sprayed with the hazardous substance, but the outdoor cleanup procedures have always worked.

Minutes later, Kelly reported that the forefinger of his right glove had a stitch poking out. He said it looked like a loop. Flight controllers in Houston scrambled to make certain the damage was, indeed, slight and superficial; they determined it was.

It was the second spacewalk in 1 1/2 weeks for Lindgren and Kelly, who's more than halfway through a U.S. record-setting yearlong flight. They got started an hour early, eager to make the home improvements.

"Going off grid for spacewalk," Kelly said via Twitter before heading out. "I'll be back w you again soon!"

Friday's excursion involved work on the space station's cooling system. The spacewalkers needed to undo jury-rigged repairs made to a leaky cooling line three years ago. The ammonia leak subsequently was fixed another way — by replacing a failed pump — so NASA wanted the radiator system back in its original setup.

Friday's leak came as Lindgren and Kelly opened and closed valves, in order to top off the ammonia coolant supply.

Their Oct. 28 spacewalk featured a robot-arm lube job and other mundane maintenance.

Kelly has been at the 250-mile-high outpost since March, and isn't due back until next March. Friday marked his 224th day in orbit, already a U.S. record. His companion for the long haul is Russian Mikhail Kornienko.

Four other astronauts are on board for the typical six months: Lindgren along with a Japanese and two other Russians.

This was the 190th spacewalk in the station's 17-year history. Astronauts have been on board, continuously, for 15 years.