Residents of Ann Arbor, Michigan, who were outside Thursday morning might have looked up at the sky to see five black helicopters soaring above, perhaps causing them to wonder why.

Some took to Twitter to share what they saw in the city that is home to the University of Michigan's main campus:

Huh. Just saw a squadron of 5 helicopters over Ann Arbor. Not sure if military exercise or just routine flying practice.

— Stephen Koller (@StephenKoller) June 11, 2015

alright so what are these 5 helicopters flying over Ann Arbor for

— lbj (@liddy__b) June 11, 2015

Why did 5 black helicopters just fly over Ann Arbor?

— Trash (@TrashTweetz) June 11, 2015

Apache helicopters flying over Ann Arbor. 5 of them total. Never have seen them flying with my own eyes before. pic.twitter.com/VzA7iFR0x7

— Aaron Zahn (@eightballham) June 11, 2015

We were out for a mid-morning walk and @mattesnyder captured these Apache helicopters flying over #AnnArbor pic.twitter.com/pcJCzvUM6f

— ssieg (@ssieg) June 11, 2015

It is unclear at this point what exactly the helicopters were doing. Earlier this year though, two deer count surveys were conducted by the city via a helicopter.

A city spokeswoman for Ann Arbor told TheBlaze in an email she didn't have any information about the flyover but did say she knew it was not related to a deer survey.

The Ann Arbor Police Department did not immediately return TheBlaze's request for comment regarding the situation.

In some cases, similar helicopters flying over cities have been conducting training missions.