After 2 days of earthquakes and cracks indicating magma was moving down the Lower East Rift Zone, the first fissure opened in Leilani Estates at about 5PM HST, Thursday, May 3, 2018.
Big Island News posted a 10PM video update with video footage accompanying a May 3 civil defense advisory:
Leilani Estates is about 11 miles downrift from Pu’u O’o, in the Puna District.
Meanwhile, increased seismicity at the summit coincided with the summit lava lake changing from inflation to deflation— this is when it began to drop (source: HVO Volcano Watch).