The attack, which took place in the village of Zawyat Abu Musalam, has heightened fears of sectarian violence, Ahram Online reported Tuesday.
The mob gathered outside a Shiite house, beat the four people inside and then set the house on fire Sunday, police said.
Egypt's ultraconservative Salafists have been accused of fueling anti-Shiite sentiment that led to the attack.
Shiite leaders are expected to hold a news conference to discuss the killings Wednesday, the head of the Misr el-Fatimiya Human Rights Center said.
N.J. man wakes up from 10-hour sleep with knife in back
Campus cop fatally shoots Texas student during traffic stop