HONOLULU (AP) — Military officials say they need more time to flush jet fuel from their Pearl Harbor water system, but some of the 4,000 military families who were displaced because of contaminated drinking water could begin returning by the end of next week.

U.S. Navy leaders addressed state lawmakers Wednesday, saying they hope to finish flushing the Navy’s system by the end of January. The Honolulu Star-Advertiser reported that the Navy said in early December it would be able to do the work in a matter of weeks.

Navy officials believe about 14,000 gallons (52,995 liters) of jet fuel spilled Nov. 20 in an access tunnel at the Red Hill Bulk Fuel Storage Facility, and some of it was sent through the Navy’s water distribution system that serves about 93,000 people.

People using the water in and near the Pearl Harbor military installation reported becoming ill, and the Navy moved many military families into Oahu hotels.

The Navy has since cleaned the spill at the aging Red Hill storage facility, which supplies fuel for many military planes and ships that operate in the Pacific. It is pumping clean water through the overall water system and the systems of all affected homes and facilities.

“The plan includes complete flushing of the entire Navy system, from the source to the faucet, with a comprehensive series of water tests in every neighborhood to certify that drinking water meets safe drinking water standards,” Navy Rear Adm. Blake Converse told lawmakers during a joint briefing.

The Navy said it will test 10% of homes, which some lawmakers questioned.

“The 10%, it is a sort of statistical determination based on past events, based on academia, based on the capacity of existing labs,” said Rear Adm. John Korka, commander of Naval Facilities Engineering Systems Command.

Korka said there is also a “confidence factor.”

Allowing families to return to their homes requires approval from Hawaii health officials.