— When investigators from the Philippine Commission on Human Rights arrived at Police Station No. 1, nothing seemed amiss.

They were working a tip about people being plucked from the slums by police, held captive at the station and ransomed for money. But as they surveyed the office of the local anti-drug unit, things looked normal: desks, two sofas, a bookshelf.

Officers assigned to the station kept glancing at the bookshelf.

With news cameras rolling and police looking on, an investigator knocked on it. Someone knocked back. When the false door was finally opened, investigators found a dozen people packed into a small concrete cell, one bloodied, one with a swollen jaw.

“How much did they want for you?” an investigator called to them.

“Forty thousand pesos for two.”

About $800.