Chinese actor Ren Quan, left, participates in the annual Beijing Marathon on Oct 19, 2014. The marathon kicked off on Sunday morning with the capital shrouded in heavy smog. [Photo/CFP]

BEIJING - The Beijing International Marathon concluded Sunday in heavy smog with Ethiopian Fatuma Sado Dergo finishing first in the 42.195-kilometer run.

The 2014 Beijing marathon went on as scheduled for the 23rd straight year despite heavy smog that has hit Beijing since Saturday.

Some of the runners wore masks, but their enthusiasm for the marathon prevailed despite the smoggy weather.

According to the organizers, the race was not called off or delayed because "46 percent of runners come from overseas or outside Beijing and there are numerous parties involved in the organizing of the competition, therefore it is difficult to reschedule the event."

However, authorities warned runners with respiratory diseases not to participate in the race. Ambulances and medical staff were prepared at the finishing point.

"I wore a mask all the way, it's the first time I've ever experienced a marathon run with a lack of oxygen," a runner said after the competition, adding that the mask had turned black after the run.

The full-race marathon was open to 26,000 entrants and the half marathon was open to 4,000.