KABUL, Afghanistan — The death toll may increase significantly from an airstrike that devastated the Doctors Without Borders hospital in Kunduz, Afghanistan, officials from the organization said on Thursday, as the search continued for 24 staff members, many of them feared to be dead.

The deaths of 12 hospital staff members and 10 patients have been confirmed in the American airstrike, with an additional 37 people wounded. Five days after the Oct. 3 attack, Doctors Without Borders was still unable to find the 24 staff members, despite having a hotline for them to call.

“We are worried,” said Guilhem Molinie, the group’s country representative in Afghanistan. “We haven’t stopped looking for them, and we’re not the only ones. Their families want to know where they are, too. We fear that some of them may be dead.”

Mr. Molinie said that there might still be more bodies in the heavily damaged main building of the hospital, but that the group had not been able to return to inspect it because of security concerns.