Tokyo and Hokkaido Prefectural Police investigators will soon question the three Japanese released Thursday after being held hostage for more than a week in Iraq to learn more about their ordeal, police sources said Monday.

Police are allowed to question them based on the revised Police Law, which gives the National Police Agency more authority to investigate crimes abroad involving Japanese citizens.

The move is based on an order issued by NPA chief Hidehiko Sato, following the trio's release Thursday.

Two of the freed hostages -- Nahoko Takato, 34, and Noriaki Imai, 18 -- live in Hokkaido, while Soichiro Koriyama, 32, is a resident of Tokyo's Suginami Ward.

They returned to Japan on Sunday and spent the night with their families at a Tokyo hotel. They are expected to return home soon and visit doctors to regain their physical and mental health.

According to one of their lawyers, they were diagnosed with posttraumatic stress disorder during health checks in Dubai, the United Arab Emirates. They need rest and should not meet reporters, the lawyer quoted doctors as saying.

Imai's grandmother, Chizue Hanada, 83, said he is having health problems.

"His health has deteriorated. I hear that he could not fall asleep until 5 a.m. this morning because of anxiety," she told reporters Monday morning in Sapporo.

A lawyer for the three told reporters Monday that Takato and Koriyama also could not sleep well.