NAIROBI, Feb. 8 (Xinhua) -- Kenyan police on Thursday interrogated 29 Ethiopians after being arrested in a security operation at Ruaraka's residential estate in Nairobi.

Kasarani divisional police commander Robinson Mboloi said the foreigners who were found being transported in a truck in Ruaraka area were to get shelter in the area before leaving for South Africa where they were promised jobs.

"The Ethiopians are under interrogation to know more about their movements. They don't have documents to warrant their being here," Mboloi said. The Wednesday's night arrest is the latest in a series to be busted by police.

Police and immigration officials have decried increased cases in which Ethiopians are nabbed in the country while on transit to either Tanzania or South Africa.

Police face difficulties in dealing with them because they cannot speak in Swahili and English.

On several occasions, Ethiopian illegal immigrants have been discovered locked up in congested rooms in Kenyan towns and cities but the trade continues to thrive even as many were repatriated.

The Kenyan authorities have blamed the vastness of the region for the runaway of the 29 foreigners into Kenya through Moyale on Kenya-Ethiopia borders

Mboloi said the driver of the lorry was also arrested in the operation. It is not clear when they left the Moyale border and how they managed to evade many roadblocks on the way.