The two tiger-raising facilities in Yen Thanh District are owned by Ho Thi Thanh, 31, and Nguyen Thi Dinh, 50.
Dozens of police officers on Wednesday morning found 14 Indochinese tigers in Thanh's basement, each weighing 200-265 kilograms, and three others at Dinh's.
The families said they had built the basements specifically to keep these tigers. Each basement spans between 80-120 square meters and is equipped with separated metal cages. Access into the basements requires passing through locked metal doors.
The tigers were transported from Laos to Vietnam as cubs, the women said. They have been kept for months, they said.
Police said neighbors of the two women were surprised to see the tigers being taken out of the houses. They said they did not hear strange sounds like tiger roars coming from there.
The tigers have been sedated and taken to a nature reserve in Dien Chau District for health checkups. Thanh and Dinh are being investigated for the alleged illegal captivity of wildlife.
Indochinese tigers are listed as endangered on the IUCN Red List. Their population is threatened by poaching for illegal wildlife trade, as some people believed their bones could be used to make traditional medicine to treat certain ailments.