According to the tweets from a worker (Happy20790) who's been at the plant from the beginning of the accident, the strange lights that were seen in TEPCO's live cam at night were from T-Hawk operating at night. The worker also says that these T-Hawks are just too light and unstable, so they are tweaking the location of the camera to somehow balance better.
(People who know about nuclear power plants have said his tweets are credible.)