GOMA, D.R. Congo — Tens of thousands of people are trying to escape the Congolese city of Goma after authorities issued an evacuation order warning that the Mount Nyiragongo volcano could erupt again.

At least 31 people have died and 30,000 were forced to flee their homes when the volcano in the Democratic Republic of the Congo (DRC) first erupted over the weekend.

Since then, the area has experienced a series of earthquakes and tremors, some that were felt as far away as the Rwandan capital of Kigali, 65 miles from the volcano in the Virunga National Park.

Significant cracks in the ground — some stretching the entire width of the road, others in the walls of buildings — have begun to appear. A resident told CNN that some of his neighbors in high-rise buildings have fled their homes out of fear that they might collapse.

"The data from seismic activity indicates the presence of magma beneath the urban area of Goma and beneath the Kivu lake," the military governor of North Kivu province, General Constant Ndima, said during a news conference on Thursday.

"Because of this data we cannot exclude another eruption on the earth or under the lake, this could arrive without any warning," he added, urging people to follow the order and warning them to stay away from the lava.

"You could die from asphyxiation or suffer serious burns," he said.

Goma is the capital of the North Kivu province, sitting at the edge of Lake Kivu on the DRC border with Rwanda. According to official projections from the United Nations, World Bank and others, the city is home to approximately 670,000 people. However, a number of non-governmental organizations in the region say the population closer to 1 million.

The initial eruption destroyed at least 900 houses and flattened five schools, according to the Norwegian Refugee Council (NRC).

The lava lake the volcano appeared to have refilled on Sunday has since cleared, according to volcanologist Dario Tedesco. The DRC government spokesman Patrick Muyaya told CNN that there was no more lava inside the volcano but the earth tremors following the eruption were unusual. "We've never seen this before, it's very surprising," he said.

The sudden exodus of people has caused major gridlock at the DRC-Rwanda border, with traffic heading away from the city at a standstill.

The eruption has damaged power and water supplies to the city. As of Wednesday, power had been partially restored, but water supplies were still cut, a spokesperson for the NRC said.

A leading humanitarian organization, the NRC has said the DRC was suffering through "the world's most neglected displacement crisis" as multiple conflicts forced 2 million people to flee their homes in 2020.

"A lethal combination of spiraling violence, record hunger levels and total neglect has ignited a mega-crisis that warrants a mega-response," NRC Secretary-General Jan Egeland in a statement. "But instead, millions of families on the brink of the abyss seem to be forgotten by the outside world and are left shut off from any support lifeline," he added.

The NRC said that a third of the country's population — 27 million people, including more than 3 million children — do not have enough food to feed themselves. — CNN