NBC: 2 Americans killed in Brussels attacks - WAFF-TV: News, Weather and Sports for Huntsville, AL

NBC: 2 Americans killed in Brussels attacks

In this image provided by Daniela Schwarzer, smoke is seen at Brussels airport in Brussels, Belgium, after explosions were heard Tuesday, March 22, 2016. (Daniela Schwarzer via AP) In this image provided by Daniela Schwarzer, smoke is seen at Brussels airport in Brussels, Belgium, after explosions were heard Tuesday, March 22, 2016. (Daniela Schwarzer via AP)

(BRUSSELS) - Two Americans have been confirmed killed in this week's Brussels attacks, a senior U.S. official told NBC News on Friday.

The official, who spoke on condition of anonymity, did not identify the two people as their next of kin were still being notified.

The source did not say whether they were killed during the twin bombings at the city's airport or the blast around one hour later at a downtown metro station.

At least four Americans have not been seen since the attacks on Tuesday. The missing include a husband and wife from the South and a brother and sister from New York City.

MORE: At least 2 Americans killed

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