Two recent in-flight emergencies involving troubled oxygen systems in the F-22 "Raptor" are unrelated to other, more worrisome breathing problems pilots have experienced for more than a year when flying the plane, according to Air Force officials.

The Air Force has been investigating why a number of F-22 pilots have experienced a mysterious loss of oxygen while in the air, causing dizziness and confusion known as hypoxia, since spring 2011.

But two recent incidents related to the F-22 oxygen system are considered regular mechanical issues not connected to the oxygen deprivation investigation, according to Air Force Lt. Col. Tadd Sholtis, a spokesman for the Air Force's Air Combat Command.

"The recent incidents that have resulted in new expressions of concern are of a different kind than the ones we have been focused on in recent months," Sholtis told CNN's Security Clearance.

Air Force officials have labeled the number of unexplained F-22 breathing incidents as "cause unknown," while labeling the two recent incidents as "cause known.

The latest problems prompted two members of Congress, Sen. Mark Warner, D-Virginia, and Rep. Adam Kinzinger, R-Illinois, to send a letter to the Air Force secretary last week demanding answers.

In an e-mail response to Security Clearance, Sholtis sent information on what Air Force initial investigations found in the two recent incidents. Sholtis said the mechanical issues were "not specific to the F-22 aircraft."

One of the incidents, an oxygen system malfunction on July 6, is still under investigation by the Air Force and the plane remains grounded, according to the Air Force information provided by Sholtis, but the incident is still listed as a "cause known" problem.

While returning from a training mission, the pilot from the 154th Wing of the Hawaii Air National Guard received a warning indication that the Onboard Oxygen Generating System (OBOGS) was malfunctioning and declared an in-flight emergency.

"The pilot experienced a hypoxic symptom in conjunction with the aircraft warning and activated the emergency oxygen system," according to the information given to Security Clearance. The pilot recovered and landed the plane without a problem after receiving emergency oxygen.