Police detained 101 Chinese nationals in separate raids on two rural homes near Colombia's capital Monday, thwarting efforts by a human-trafficking ring to smuggle them into the United States, authorities said.

Authorities said police, acting on tips by local residents, found the Chinese immigrants being held like prisoners in overcrowded conditions, with dirty mattresses and food remains strewn across the floor of the homes.

"The house was locked and they were unable to leave," said Edgar Castillo, government secretary of Zipaquira, a town 30 kilometers (18 miles) north of Bogota.

Among the 42 apprehended during the first raid, 21 entered Colombia legally, on 15-day tourist visas, after having arrived to Bogota on an Air France flight from Italy on March 30 and 31, said Castillo, who had access to the foreigners' passports.

The remaining 21 arrived a week later by the same airline, though both groups appeared to have initiated their cross-continental journey in Cambodia, he said.

None of the 59 seized in the second raid were carrying documents.

Authorities for Colombia's DAS domestic intelligence agency, which is in charge of immigration, were interviewing the mostly young adult males at Zipaquira's police station and were unable to comment on their legal status, a DAS spokesman told The Associated Press.

The two groups were likely victims of an immigrant-smuggling ring who promised to shepherd them to the United States using Colombia as a way station, authorities said.

"There's no reason if they entered Colombia as tourists to be living in these conditions closed off from the outside world," Col. Wilson Laverde, police commander in Cundinamarca state, told The Associated Press. Zipaquira is located in Cundinamarca.

Although no arrests have been made, police are interrogating a Costa Rican national who arrived to the home where the Chinese were being held shortly after the first police raid, Laverde said.

A similar raid last month, in which police discovered 19 Chinese immigrants near the southern city of Cali, raised concerns among authorities that Colombia is being used as a transit point for human trafficking rings from China.

Foreign Minister Fernando Araujo said last week the government would revise its entry requirements for Asian nationals after saying the government had detected an important flow of human traffic from China "that doesn't correspond to investors or tourists, but people who are in transit to other countries."