Ottawa says it is aware of reports that another Canadian citizen has gone missing in the Gaza Strip.
Global Affairs Canada says it is providing consular assistance to the family but can't share more because of privacy considerations.
The Associated Press reports that Israeli forces detained two young adult American brothers and their Canadian father in Gaza in an overnight raid.
Relatives of the men say they were taken from their home.
A U.S. Embassy official in Jerusalem reached by telephone from Washington said American officials were aware of the situation and were following up with Israeli authorities.
The embassy official gave no details and ended the call without giving her name, while the Israeli foreign ministry and military had no immediate comment.
Borak Alagha, 18, and Hashem Alagha, 20, two brothers born in the Chicago area, are among fewer than 50 U.S. citizens known to still be trying to leave sealed-off Gaza, as the Israel-Hamas war entered its fifth month.
Cousin Yasmeen Elagha, a law student at Northwestern University, said Israeli forces entered the family home in the community of al-Muwasi, near the southern city of Khan Younis, around 5 a.m. Gaza time Thursday.
The soldiers tied up and blindfolded the women and children in the family, and placed them outside the home, the cousin said.
The two American brothers, their Canadian citizen father, a mentally disabled uncle and two other adult male relatives were taken away by the Israelis, and remain missing, Elagha said.
Men of a neighboring household were also taken away. So were other adult male relatives of another Alagha household, for a total of about 20 detained, the U.S. cousin said.
A family social media account from Gaza also described the detentions.
State Department spokespeople in Washington had no immediate comment on the reported detention of the American brothers.
The brothers would be among three American citizens taken into custody by Israeli forces this week, during the same time Secretary of State Antony Blinken visited the region to try to mediate a ceasefire and hostage release deal with ally Israel and regional Arab leaders.
