NASA engineers say they are closing in on the cause of a water leak inside the spacesuit of Italy's first spacewalking astronaut that could have drowned him.

NASA has been investigating the July 16 close call outside the International Space Station, when astronaut Luca Parmitano reported water leaking into his helmet, at the back of his head.

When the flowing water, about 1 to 1.5 liters, began clogging his ears and covering his eyes and mouth, ground controllers aborted the spacewalk.

After first suspecting the suit's drink bottle or cooling tubing that circulates water through the suit's undergarment, investigators now are focusing on the suit's life support system, USA Today reported Tuesday.

Engineers "are looking at what steps to take next, this week," NASA spokeswoman Brandi Dean said. "They actually have isolated the failure to the spacesuit's Primary Life Support System, which is essentially the backpack of the suit."

NASA quickly shipped a spacesuit repair kit to Kazakhstan last week so it could be launched to the station aboard a robotic Russian space freighter that docked with the ISS July 27.