Police are investigating how two dirt bike riders were knocked off their bikes near Kaikohe in Northland, leaving one dead and another with serious injuries. Officers were called to Ngapipito Rd about 11.10pm yesterday following reports of a serious incident. One person was found dead at the scene. Police said they were in the early stages of the investigation, but believed two people were knocked off their dirt bikes: one on Ngapipito Rd, south of Kaikohe and the other on Tana Rd, west of Moerewa. The second rider was taken to hospital with serious injuries. Investigations were under way. Ngapipito Rd was closed between Mangakahia Rd (SH15) and the intersection of Tana Rd, Moerewa, and expected to remain closed for some time. Motorists were advised to avoid the area. 'No-one really knows' A community leader urged people to wait for the facts rather than passing on rumours.…