Two Arab Israeli nursing students have been arrested on suspicion they failed to tell authorities about an impending homicide bomb attack on a bus they were traveling on, police said Wednesday.

The two women, both 19, got off the bus Sunday after the Palestinian assailant told one of them that "something horrible" was going to happen, said Ilan Harush, a local police chief in northern Israel.

Twenty minutes later, the bomber set off the explosives he was carrying, killing himself and nine passengers.

Based on witness accounts, police began a search for the women, who live in northern Israel. They were arrested earlier this week and charges will be filed against them Thursday.

"We say that every citizen who has such information has to immediately inform police and rescue officials," Harush told Israel Radio.

If police had known, they could have stopped the bus earlier and four people who were killed outside the bus when it exploded could have been saved, Harush said.

The women are cooperating with investigators and said that they did not think they had to inform police, Harush said.

Several Arab Israelis -- who have citizenship and comprise about 20 percent of Israel's population -- have been killed in suicide bombings in recent months. There have been no previous reports of suicide bombers reporting to passengers about an impending bombing.