As senators say they didn’t know about the presence of U.S. troops (or the number of them) in Niger, some are calling for a review of how Congress gets notified of such actions.

Pennsylvania Democratic Sen. Bob Casey is among the lawmakers who in recent days have said on television they were unaware of the activity in Niger, despite a formal letter about U.S. forces in the region that went to Capitol Hill months ago.

“When you consider what happened here, the four sergeants lost their lives, I think there’s a lot of work that both parties and both branches of government need to do. Not only to stay more informed but to focus on why we’re there and what happened to get to the bottom of this,” Casey told CNN on Monday.

Senate Minority Leader Charles E. Schumer said Sunday he was not aware of the scope of the operations in Niger. The New York Democrat suggested reopening the authorization for use of military force debate.

“We are in a brave new world, you know, there are no set battle plans. You don’t declare war and then fight three weeks later. But having said that, the Constitution says Congress has the power to declare war, and if you’re in a long-term war, Congress ought to keep that ability. So we need to re-examine this. We’re on a AUMF that extends 16 years, from right after we were attacked at the World Trade Center. So I would be for re-examining it,” Schumer said on NBC’s “Meet the Press.”

Little is publicly known about the deaths of four U.S. soldiers in the West African country, but the reality of American boots on the ground should not have been such a surprise.

Congress was notified of the U.S. work on counterterrorism in the Lake Chad Basin region of Africa, which, as of June 6, included about 645 servicemembers in Niger itself. It’s likely many members of Congress did not read that notification.

It came in a routine letter sent by President Donald Trump to Speaker Paul D. Ryan of Wisconsin and Sen. Orrin G. Hatch of Utah in his capacity as president pro tempore of the Senate.

The June letter also referenced U.S. activity in Somalia against the terrorist group al-Shabab, the basing of U.S. forces in Djibouti for actions in the region, and the better-known actions in places such as Iraq and Afghanistan.

As for the details of what happened in Niger, the Senate Armed Services Committee is looking for more information.

Senate Armed Services Chairman John McCain said during an appearance Monday on ABC’s “The View” that he was still battling with the Trump administration for more details.

The Arizona Republican said the panel was not getting enough information about the operations. His remarks came after he met with Defense Secretary James Mattis on Friday.

South Carolina GOP Sen. Lindsey Graham said McCain, his friend and frequent ally, would be working to solve the problem of insufficient information when U.S. military personnel are killed overseas.

“We don’t know exactly where we’re at in the world, militarily, and what we’re doing. So John McCain is going to try to create a new system to make sure that we can answer the question why were we there, we’ll know how many soldiers are there, and if somebody gets killed there, that we won’t find out about it in the paper,” Graham said on “Meet the Press.”