A criminal gang is demanding $1m per head for the safe return of kidnapped missionaries and children.
Justice Minister Liszt Quitel confirmed that a demand had been received for the release of the group of 17.
They were abducted on Saturday morning on their way to the airport at capital Port-au-Prince after visiting an orphanage in nearby Ganthier.
The group, which includes five children, belongs to the US-based Christian Aid Ministries, which provides practical assistance to places impacted by poverty and natural disasters.
There are 16 Americans and one Canadian in the group.
"The demand was made to the country chief of the Christian Aid Ministries — they asked for $1 million per person," Quitel told The New York Times.
"Often these gangs know these demands cannot be met and they will consider a counteroffer from the families, and the negotiations can take a couple of days sometimes, or a couple of weeks."
The missionaries were ordered off their bus in the Croix des Bouquets area and taken by the notorious 400 Mawozo gang, which has a history of kidnappings for ransom.
Quitel told CNN, "The kidnappers have been warned about harming the hostages and what may be the consequences for them [if that were to happen]. But they are not swayed by those warnings."
According to CNN, 400 Mawozo largely controls Croix des Bouquets, and that five priests and two nuns were abducted in the same area in April before being freed after a ransom was paid.
Christian Aid Ministries is asking people to pray for the group's safety.
"Join us in praying for those who are being held hostage, the kidnappers, and the families, friends, and churches of those affected. Pray for those who are seeking God's direction and making decisions regarding this matter," it said.
"As an organization, we commit this situation to God and trust Him to see us through. May the Lord Jesus be magnified and many more people come to know His love and salvation."
White House Press Secretary Jen Psaki said on Monday that the State Department and FBI were working to secure their release.
"The President has been briefed and is receiving regular updates on what the State Department and the FBI are doing to bring these individuals home safely," Psaki said.
"The FBI is part of a coordinated US government effort to get the US citizens involved to safety. Due to operational considerations, we're not going to go into too much detail on that but can confirm their engagement.
"And the US embassy in Port-au-Prince is coordinating with local authorities and providing assistance to the families to resolve the situation."