A key airport in southwest China's Sichuan Province reopened on Monday morning after thick fog affected 131 flights and stranded about 13,000 passengers.

The Shuangliu International Airport in Chengdu, capital of Sichuan, resumed operation at about 10:42 AM after a four-hour shutdown.

The fog reduced visibility to less than 20 meters early Monday morning, far less than the minimum 500 meters required for take-offs, according to the airport administration.

Ten flights were canceled and 121 others were delayed. A flight from Singapore was diverted to Kunming, capital of Yunnan Province.

Airport staff were trying to arrange additional flights to move the passengers, but some people were likely to be delayed until after midnight.

Meteorologists said the fog formed after rain on Sunday was followed by strong sunlight Monday, and they said there might be more fog Tuesday.

It was the third closure of the airport in a month caused by fog. The previous closures, in the second half of January, affected nearly 200 flights and stranded more than 15,000 passengers.

The airport is one of the busiest transport and distribution centers in southwest China.