A Navy official says he’s optimistic that displaced families will be back in their homes and able to safely use the water supply by Christmas, but that message runs counter to the more cautious tone struck by an Army commander who says recovery from the crisis is uncertain and could take weeks.

Every branch of the military has been active in the response to the contamination of the Navy’s water supply on Oahu, but it is unclear how many military families have been displaced.

During a joint session of the state Legislature, Navy officials Friday said that they were responsible for the contamination of the system that serves 93,000 people — mostly military service members and dependents—but expressed optimism that the crisis would come to an end soon.

“After evaluation of the testing results, we will work closely with the Department of Health and other stakeholders to be able to declare our waters safe and get people back in their home. My goal is to get this done by Christmas,” said Rear Admiral Dean VanderLey, commander of Naval Facilities Engineering Systems Command Pacific.

But just hours before on Friday morning, during a Facebook live town hall meeting, Army 25th Infantry Division commander Maj. Gen. Joseph Ryan gave residents of Army housing areas affected by the contamination of the Navy’s water supply a more sobering assessment, telling them that it would take at least six to eight weeks “at best” before it would be safe to return to their homes.

“I am disappointed to tell you, but I have to be honest with you, to tell you that we’re not going to be able to move you back into your homes for Christmas,” Ryan said, “That is disappointing to all of us. We had hoped to get to a solution that would allow for otherwise, but that is not going to be the case.”

Ryan emphasized that any resident of an impacted area should not use or touch their water for any reason regardless of whether they smell contamination.

The Army assembled Task Force Ohana on Dec. 2 to provide aid to families living on Aliamanu Military Reservation and Red Hill military housing at the direction of U.S. Army Pacific commander Gen. Charles Flynn. Troops have been passing out water, doing medical screenings and moving families into hotels. Ryan returned early from a large-scale training exercise in Japan to help oversee relief efforts.

As of Friday the Army had entered contracts with hotels for 2,300 hotel rooms, and 1,300 had been claimed.

Brig. Gen. Kirk Gibbs, U.S. Army Corps of Engineers Pacific Ocean Division, said that the Army has brought in personnel and specialists from outside of Hawaii to assist with efforts, including Army Environmental Command head Col. Alicia Masson in San Antonio, Texas, and personnel from U.S. Army Material Command in Alabama.

The Navy now maintains that the contamination came from a 14,000 gallon spill of fuel and water from Red Hill Fuel Storage Facility’s fire suppression system on Nov. 20, which it says was cleaned up by Nov. 23.

“I am confident that the source is the 20 November spill, and that source was removed within approximately 24 to 30 hours. I also have a strong theory based on technical rigor and engineering analysis on how that fuel got into the shaft,” VanderLey told lawmakers. “The good news is that this was a singular event.”

However, Army officials told residents that they can’t be sure what the scope of the contamination is and are ruling nothing out.

“The affected area continues to expand because we just simply don’t know in certain cases where this is bounded, and we want to err on the side of caution,” said Ryan.

The military is currently setting up the Oahu Military Contamination Registry of military housing residents who could have been affected.

“The whole idea is that we don’t know how much is ultimately going to be affected, so we’re not going to call it AMR/Red Hill. It’s going to be Oahu,” said Maj. Gen. Michael Place head of the Army’s 18th Medical Command.

Place said that Task Force Ohana’s medical component has been talking to roughly 600 people a day to screen them for symptoms. Medical personnel from each military branch are all working on the response. But Place admitted that the military’s medical staff is playing catch up and facing a situation most never have dealt with before.

“There’s actually very limited research in terms of petroleum contamination and exposures and so forth,” Place said. “We don’t devise studies to feed people petroleum products, and then see what happens, that would be unethical.”

He said that most studies have looked at acute exposure to petroleum, and that those studies suggest that recovery is usually swift and with relatively few complications. But Place stressed that the Army doesn’t know that that’s the case with the current contamination and it’s unclear how long the water has had petroleum in it.

“The bottom line is what I’m telling folks is that we don’t know,” said Place. “We don’t know how much of an exposure you may potentially have had and we don’t know what the medical consequences of those are.”

U.S. Army Garrison Hawaii commander Col. Dan Misigoy said that Army Emergency Relief has issued about $709,000 in grants to assist affected families. The AMR and Red Hill housing areas are Army administrated, but have families from each military branch living in them.

Ryan said that the Army is setting up an assistance center at Fort DeRussy to assist families that have been temporarily relocated to hotels in Waikiki.