Story highlights Sen. John McCain is the chairman of the Senate armed services committee

The Arizona Republican said Wednesday "We deserve to have all the information."

(CNN) Sen. John McCain said Thursday that he might seek a subpoena to gain the information he wants about the attack in Niger that left four US soldiers dead and two wounded.

"It may require a subpoena," McCain told reporters on Capitol Hill when asked what steps he would be willing to take to get more information.

The Defense Department is conducting an initial review of the deadly incident, searching for precise answers as to how 50 ISIS-affiliated fighters were able to ambush a group of soldiers two weeks ago.

McCain, who is the chairman of the Senate armed services committee, said he might not wait for the department to finish its own investigation before seeking those details.

"That's not how the system works. We're coequal branches of government," McCain told CNN's Suzanne Malveaux. "We should be informed at all times."

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