Amid reports of fresh attacks by Boko Haram, killing hundreds of villagers, Nigerian police today offered a $300,000 reward for any information leading to the rescue of more than 200 girls kidnapped from their dormitories 23 days ago.
A team of about 10 US military personnel - specialists in logistics and intelligence - also are scheduled to arrive to the region in the coming days.
Religious leaders from Nigerian-American churches held a news conference in Washington today to call for even stronger international action to free the kidnapped girls and to stop Boko Haram, the Islamic terrorist group that took responsibility for the abductions.
"We have the hope that they can be found because they are not being killed. They are being sold off as sex slaves. They are being sold off for $12 for a mass marriage to Islamic leaders," said James Fadele, president of Christian Association of Nigerian-Americans. "This can no longer happen in this day and age. They can track them down, they can find them out and they can be brought back home."
The challenge, however, is enormous.
The search will focus on the Sambisa forest, where it is thought the students were taken. It is a remote, rugged wilderness that is eight times the size of Yellowstone National Park, making the search even more difficult because it is believed that the girls have been split up.
Photos: The kidnapped Nigerian girls.
"I think the one thing that's almost certain is the young girls are no longer together," said retired Gen. Carter Ham, former head of US Africa Command. "They almost certainly are dispersed in small groups or even individuals."
Some may already be out of the country or sold into slavery.
That is what happened to one young woman who spoke to ABC News. She said she was taken last year by Boko Haram and held for three months, dragged through rocky paths and forced to sleep in caves.
She said she faked an illness and escaped during a trip to the hospital.
State Department spokesperson Jen Psaki said today the US ambassador to Nigeria had met with the national security adviser there, and the legal attaché has been in touch with Nigerian police.
She also said the FBI and USAID both stood ready but both countries were working out exactly what the US could do.
ABC News' Hamish MacDonald, Bentson Clark, Bartley Price and Ali S. Weinberg contributed to this story.