In a country where media is state-controlled and heavily censored, Lu’s work has long revealed a side of China that carries a risk of chafing authorities. Portraits of coal miners, AIDS patients, and drug addicts as victims of China’s economic rise are subjects Beijing may consider "sensitive."
Most recently, Lu’s work for Greenpeace has focused on pollution and how development has steadily poisoned China’s landscape and its people.
Greenpeace declined to comment on his disappearance.
However, Amnesty International, Human Rights Watch, and the Committee to Protect Journalists have all called on China’s government to clarify what happened to Lu.
"Chinese authorities must immediately account for Lu Guang's whereabouts, allow him to travel freely, and halt the harsh measures taken against journalists throughout the country," said Steven Butler, Asia program coordinator for the Committee to Protect Journalists. "Lu's detention is a high-profile illustration of the cruel and arbitrary way that China detains journalists and other civilians in Xinjiang."
Beijing is facing mounting international pressure over Xinjiang, where the state maintains a network of detention facilities or so-called "re-education" centers.
An estimated one million Chinese Muslims, mostly from the Uighur minority, have disappeared into the camps across Xinjiang in what rights groups have called the biggest mass internment of civilians in the world today.
In a recent interview with NBC News in Kazakhstan, a former detainee at one of the camps described prison-like conditions and political indoctrination with patriotic songs and lessons in Chinese laws and loyalty.
“They brainwash us,” said Kairat Samarkand, 30, referring to his nearly four months in detention. “If you break their rules they will punish you.”
Samarkand said detainees were divided into three categories according to their perceived offense: those who were religious, those who have traveled abroad, and petty criminals.
After long denying the detention facilities existed, Beijing has launched a propaganda campaign to portray the camps as benign "job training centers" aimed at fighting extremism in a region it considers vulnerable.
Foreign journalists travelling to Xinjiang, including a NBC News team, have been routinely detained and followed by security agents and police who monitor, prevent and obstruct reporting on the internment camps.
Lu was honored as a winner at the 2004 World Press Photo competition for his expose of “AIDs villages” in Henan province, where people infected with HIV after selling their blood were forced to live in poverty. His expose prompted the central government to act. In 2015, he took third place for his ongoing “Development and Pollution” series.
“The reality in China is you never know if you’re going to get into trouble because there are no written rules,” Lu said in an interview last year with FT.com. “The only way to find out if something is permissible is by doing it.”