They probably lost a nuke in the area. Wouldn't be the first time.

speculations are it's either related to ICE or drug cartel investigations

The former has a long history of not cooperating with local authorities (also in ways I personally think are sometimes quite malicious but that is off topic). Und normal circumstances ICE would never have the power to lead to a shut down of air space, but with the current administration who knows.

And drug cartel investigations won't cooperate with the city council as an investigation big enough to shut down airspace wouldn't want to risk it leaking by speaking with a city council about it.

But this is a pretty big deal and lets hope this is just about preventing some high ranking drug cartel members from fleeing and not some retaliatory horror story implicitly triggered by the repeated public rejections and denouncements of Trump in recent week. Like if we look at full (and violent) dictatorships(1) you would expect an internet outage to follow and then a lot of people to die.

(1): To be clear no the US is not a full blown violent dictatorship. Even through things are bad, they are not "that" bad. Through IMHO there seem to be people in the government which want to make it exactly that bad.