Heavy security presence today - any particular reason?

Today I rode the L downtown and almost from the start I noticed an unusually large number of regular and K-9 police units patrolling the platforms. At the Roosevelt Road elevated station it was almost ridiculous, at least 8 uniformed CPD officers with 3 dogs, all bunched together talking. At Clark/Lake there were 4 officers with 2 dogs (all hanging out near the turnstiles). Anyone know a particular reason for the beefed up police presence today or can it be attributed to a "random" show of force?

Well as you know it's because of what happened in London. And you said there was no security precense in CTA there right after the London Bombings? Wow, I'm surprised, they should have increased security there when London happened. I hope the L keeps their security presence at high level for a while, like NYCTA and my T system in Boston.