The fire destroyed at least 10,000 shelters as it tore through the camp, according to the Inter Sector Coordination Group (ISCG) in Bangladesh.
Up to 10,000 Rohingya refugee families -- more than an estimated 45,000 people -- have been displaced, the ISCG said, who also warned that figure could climb in the next few days as assessments from aid organizations continue.
Essential facilities including hospitals, distribution points, learning centers, and women's support services were also damaged in the fire along, ISCG told CNN.
The Bangladesh Red Crescent Society said Tuesday that it is launching one of its "biggest ever rescue and relief efforts" in the camp.
On Monday evening, fire services, Bangladesh's Refugee Relief and Repatriation Commissioner, and rescue and response teams battled the fire in an attempt to prevent its further spread, the UN refugee agency UNHCR said.
"I am deeply concerned by the impact of a terrible fire today in Cox's Bazar, Bangladesh," Vitorino said, adding that "IOM teams and partners are working together to respond to the crisis and ensure the safety and well-being of all."
Images from witnesses showed a massive blaze consuming huts and scores of refugees fleeing on foot. The cause of the fire has not yet been determined.
"The fire spread so quickly that before we understood what happened, it caught our house," said Tayeba Begum, a Save the Children volunteer who witnessed the fire. "People were screaming and running here and there. Children were also running scattered, crying for their family. It is the most horrific incident I have witnessed recently."
"It is another devastating blow to the Rohingya refugees who live here. Just a couple of days ago we lost one of our health facilities in another fire. The risks of fires in these extremely densely populated and confined areas are enormous," Van Manen said.
Estimates of the number of Rohingya refugees living in Cox's Bazar range from 800,000 to more than 900,000, according to the UNHCR and Save the Children.
In 2016 and 2017, Myanmar's military launched a brutal campaign of killing and arson that forced more than 740,000 Rohingya minority people to flee into neighboring Bangladesh, prompting a genocide case to be heard at the International Court of Justice. In 2019, the United Nations said "grave human rights abuses" by the military were still continuing in the ethnic states of Rakhine, Chin, Shan, Kachin and Karen.
Myanmar denies the genocide accusations, and maintains the "clearance operations" by the military were legitimate counter-terrorism measures.