The Pentagon has not yet concluded what happened to Sgt. La David Johnson and why his body was found two days after a deadly ambush of U.S. troops in Niger, members of the Senate Armed Services Committee said Thursday following a classified briefing.

The fate of Johnson and a firm timeline of the attack remain among major questions that the senators said were unanswered during their meeting with an assistant defense secretary and a general with the Joint Chiefs of Staff on Capitol Hill.

“Why did it take 48 hours to find Sgt. Johnson? We don’t know that yet and I take it that the guys down there briefing us didn’t know that, that they haven’t drawn that conclusion from [U.S. Africa Command] headquarters,” said Sen. Bill Nelson, D-Fla., a senior member of the committee.

The briefing came after weeks of public pressure on the Pentagon and the Trump administration to explain how four soldiers were surprised and killed by about 50 Islamic State-affiliated fighters in the West African country on Oct. 4.

Sen. John McCain, R-Ariz., who pressed Defense Secretary Jim Mattis to provide more information on the incident to Congress, said there are still “100 questions that need to be answered,” including what happened to Johnson, but that the Pentagon is being more forthcoming.

“It’s progress. We expect more, but this is what we’ve been asking for,” McCain said.

The investigation into the incident by AFRICOM is expected to take about 30 days and many of the questions could be answered at the conclusion, according to senators.

“I emerged with more questions than answers and there needs to be a full investigation,” Sen. Richard Blumenthal, D-Conn., said. “I need to be able to look families in the eye and explain what our mission is, what mistakes were made in this incident, and were mistakes made, who made them and why.”

Blumenthal said he wants public hearings in the Senate to look into the incident in Niger and the U.S. military role in the region.

“The American people need to understand why we have 6,000 troops in Africa,” he said.