Newark Fire Department Battalion Chief Michael Witte says the three were walking over a sidewalk grate when smoke and flames rose up. Witte says none of the injuries was life-threatening.
Public Service Electric & Gas spokeswoman Karen Johnson says about 250 customers in downtown Newark are without power.
There's no word when electricity will be restored.
Among the buildings without power is the Martin Luther King Federal Courthouse. The outage forced postponement of a bail hearing for a New Jersey blogger charged with threatening three federal judges in Chicago. A new date has not been set for the hearing for Harold "Hal" Turner.