Update, Sept. 16, 2017, 9:15 a.m. PT: Police arrested an 18-year-old man in Surrey on Saturday, Sept. 16, in connection with the London Underground bombing at Parsons Green. He is expected to be moved to London later and we will continue to share more details as they become available.
Update, Sept. 15, 2017, 12:30 p.m. PT: Following an earlier explosion on the London Underground, the terror threat level in the UK has now reportedly been raised from "severe" to "critical," suggesting authorities are on alert for any further attacks. We will continue to update our story as new information becomes available, but here's what we have learned so far:
Original post: On the morning of Sept. 15, an explosion occurred on a London Underground train during rush hour, and authorities are treating the incident as a terror attack. Here's what we know so far about the incident:
This is a developing story and will be updated as new information becomes available.