A secret memorandum that expanded intelligence sharing with Israel after the Oct. 7 Hamas attack has led to growing concerns in Washington about whether the information is contributing to civilian deaths, according to people familiar with the issue.

Among the worries is that there is little independent oversight to confirm that U.S.-supplied intelligence isn’t used in strikes that unnecessarily kill civilians or damage infrastructure, the people said.

The U.S. doesn’t share intelligence specifically intended for ground or airstrike operations in Israel’s military campaign in Gaza, the people familiar with the issue said. However, Israel is responsible for certifying its own compliance, and in some cases does so orally, officials said. In addition, they said, it is hard to know how U.S.-provided intelligence is used once it is combined with Israel’s own data.

When Washington shares intelligence with allies, it first assesses what a partner could do with that information—such as conduct a strike—and decides whether it would be legal for the U.S. to do the same. Based on that determination, the U.S. may ask for additional assurances from the ally on what it would do with the intelligence before sharing it.

But Sarah Yager, Washington director of New York-based nonprofit Human Rights Watch said the intelligence-sharing arrangement has little in the way of rules and restrictions and “essentially opens up the entire U.S. vault.” Separately, the administration is weighing assurances from Israel that U.S.-provided weapons are used in accordance with humanitarian law and isn’t blocking U.S. or U.S.-supported humanitarian aid deliveries, U.S. officials said.