Israel is to fly a first planeload of South Sudanese deportees home on Sunday with more expected to follow later in the week, a spokeswoman for the Population and Migration Authority said.
"We have about 150 so far (for Sunday's flight)," Sabine Hadad told AFP on Wednesday. "We want more planes (to go) during the week."
On Tuesday, the authorities arrested 100 illegal immigrants, while another 300 people agreed to be repatriated voluntarily, she said, without saying which countries they were from.
She had no updated figures for Wednesday morning's raids.
Signup to our newsletter and follow us on Facebook and Twitter!
Official figures show there are 60,000 Africans living in Israel illegally, most of them in run-down neighbourhoods of south Tel Aviv.
Until last week, the estimated 1,500 South Sudanese living in Israel were protected from deportation by a policy which afforded them "temporary protection."
But last Thursday, a Jerusalem court overturned that long-standing policy, ruling that they were no longer at risk in their homeland and clearing the way for their mass expulsion.
Israeli daily Haaretz said on Wednesday that a delegation of South Sudanese immigration officials was expected in Israel this week to coordinate repatriation of their citizens.
Rising tensions over the growing number of illegal immigrants in Israel exploded into violence last month when a protest in south Tel Aviv turned nasty, with demonstrators smashing African-run shops and property, chanting "Blacks out!"
Israel, which reportedly backed South Sudan through its 1983-2005 war with Khartoum, recognised the new nation and established full diplomatic relations with its government shortly after it declared independence in July last year.
The Jewish state does not have relations with Sudan, which it has accused of serving as a base for Islamic militants.