HONOLULU -- The military said it is still trying to figure out why a F-15 fighter jet crashed into the ocean on Friday.

The Air Force and National Guard said they are assembling a team of experts to begin their probe.

KITV's Catherine Cruz reported that the $28 million jet is on its way to the ocean floor about 60 miles off Oahu.

Some debris from the crash site was retrieved Saturday, officials said, but they said it's unclear how much of what was brought back to Honolulu harbor will hold any clues to the cause of the downed jet.

A special team of investigators said it is looking into what caused an F-15 to lose altitude while on a routine training mission off Oahu.

The U.S. Coast Guard rescued the pilot who was forced to eject as the plane went down.

Saturday afternoon, some crash debris, including the lift raft the pilot used, was brought back to Honolulu.

It's not clear if the crash will prompt any further inspections of the jet fighters across the world, officials said, but in Hawaii, Gen. Robert Lee said the Guard's F-15s will not be running any more training missions until further notice.

"As far as the future, we will have to see where the investigation takes us," Lee said.

The F-15s are charged with guarding Hawaii's air space, and Lee said, should there be a problem, the two jets that are on daily alert will be put into action.

One of its major missions is to provide air security, especially since 9/11, and the 199 squadron sat alert every day to provide air defense for the state of Hawaii.

The F-15s sat grounded following a Missouri crash that revealed structural problems with the fighter jets, officials said.

Just last month, Hawaii got the OK to resume flying its fleet of F-15s with the exception of seven jets.

They remain off limits because of what the military called discrepancies uncovered during the inspection stand-down.

The guard said the crash investigation could take about a month.

The pilot won't be flying while this probe is under way, officials said.

Besides a debriefing with the rescued man, investigators said they will be analyzing all radio transmissions and inspection records leading up to the ill-fated flight.

The U.S. Coast Guard said a final check of the crash site Saturday morning indicated that there is little pollution in the area.

Any jet fuel in the water has since dissipated, officials said.