XINING, May 15 (Xinhua) -- Police in northwest China's Qinghai Province said they have detained five suspected tomb raiders and are attempting to locate eight missing cultural relics.

Of the five suspects, two were part of a grave robbery gang that was caught on May 6. Qinghai police arrested 13 members of the gang in March over suspected illegal excavations in Dulan County on the Qinghai-Tibet Plateau.

Police said another suspect remains on the run.

On May 8, three suspects from another tomb robbery gang were also caught in Dulan.

The investigation is ongoing.

Dulan has more than 2,000 ancient tombs dating back to between the 7th and 8th centuries.