Iranian police are reported to be investigating complaints that two Chinese and a Taiwanese marathoner may have had their water spiked with the date rape drug Rohypnol during an expedition along the Old Silk Road.

Organizers of the expedition say the three became “tired and disoriented” while running through Iran early Monday and were taken to a hospital. All were released after treatment and were expected to resume their run Tuesday.

Organizers said Iranian police are seeking to determine whether the powerful sedative Rohypnol, also known as Flunitrazepam, was slipped into the runners' water by an Iranian driver who was angry at being fired.

The expedition was organized by Taiwan ultramarathoner Kevin Lin to raise public awareness about water shortages. He and Chinese runners Bai Bin and Chen Jun are following a 10,000-kilometer route from Turkey to Xian, China.