A mother from Evanston and her daughter who were visiting Israel are missing, and family members fear they have been seized by Hamas militants.

Natalie Raanan, 18, and her mother, Judith, 59, have not been heard from since around noon Saturday, the day Hamas launched its offensive, according to family. They were last in Nahal Oz, a kibbutz about 1.5 miles from the Gaza border that was attacked by militants.

The two U.S. citizens landed in Israel in early September to celebrate the High Holidays and visit relatives, family said. They added that they want the United States government to do everything in its power to secure their release. 

Judith Raanan was a member of Chabad of Evanston, which posted a message on Facebook Sunday asking the community to pray for her and her daughter.

Hamas and other militants in Gaza say they were holding more than 130 soldiers and civilians captured from inside Israel.

Around 900 people, including 73 soldiers, already have been killed in Israel, according to media reports. In Gaza, more than 680 people have been killed, according to authorities there; Israel says hundreds of Hamas fighters are among them. Thousands have been wounded on both sides.

On Monday, President Joe Biden announced that the U.S. death toll in the war has gone up to 11 and an undetermined number remain unaccounted for. It was not yet clear if the missing are dead, in hiding, or had been taken hostage.

Biden said the U.S. believes it is likely that American citizens may be among those being held hostage by Hamas, but officials are working to confirm that.

“I have directed my team to work with their Israeli counterparts on every aspect of the hostage crisis, including sharing intelligence and deploying experts from across the United States government to consult with and advise Israeli counterparts on hostage recovery efforts,” Biden said in a statement.

Hamas spokesman Abdel-Latif al-Qanoua told the AP that the group’s fighters continued to battle outside Gaza and had captured more Israelis as recently as Monday morning.

He said the group seeks the release of all Palestinian prisoners held by Israel, which in the past has agreed to lopsided exchange deals in which it released large numbers of prisoners for individual captives or even the remains of soldiers.

Among the captives are soldiers and civilians, including women, children and older adults, mostly Israelis but also some people of other nationalities.

On Sunday, the U.S. dispatched an aircraft carrier strike group to the Eastern Mediterranean to be ready to assist Israel, and said it would send additional military aid.

Contributing: Associated Press