The passengers, hailing from Mumbai, were on a visit to their native Nadol village in Pali district when the mishap occurred near Purada.
"We have registered a case against the trailer driver who fled the spot after the accident. He was later arrested," SHO Sumerpur, Sumer Singh said.
The deceased persons are Madan Kumar (52), Dinesh Kumar (40), Narendra Kumar (48), who are brothers, and their cousin Meghraj (48) from Ahmedabad, investigating officer in the case Meetha Lal Parmar said.