The tourists, a group from central Russian city of Yaroslavl, set out on a hiking expedition May 1 but never reported back.
"At 11 a.m. local time (7 a.m. GMT) parts of a watercraft have been found near the [group's] temporary camp," said Sergei Sergeyev, a spokesman for the emergency services in the Republic of Adygea. He added that an oar had also been found some two kilometers (1.2 miles) downstream of the camp.
The group left the southern resort of Sochi May 1 to travel along the river Belaya to the regional capital, Maikop, where it was scheduled to take plane for Yaroslavl. The search started May 17 after relatives reported that the group had failed to arrive as planned.
Sergeyev said Friday five rescue teams and a helicopter were involved in the ongoing search operation for the group in the republic, whose capital is about 1,000 miles south of Moscow.