Fires burned out of control Friday as a volcano sent 200-foot-wide rivers of lava flowing through the center of Goma, setting off explosions, destroying homes and forcing tens of thousands of people to flee.

Officials were trying to determine the number of casualties amid concerns there could be many dead, since at least 14 villages north of Goma were destroyed by three rivers of lava flowing from Mount Nyiragongo. But amid the chaos of the area, located near the Rwandan border, there were no immediate reports of deaths.

A large explosion set off by lava destroyed the main fuel depot in Goma, a port on the northern end of Lake Kivu. Streams of lava flowing from the volcano 30 miles to the north and emptying into the lake damaged 80 percent of Goma and put its airport out of commission, said Florian Westphal, the Red Cross regional information officer.

"Right now, we have no office or home because they were destroyed by the lava," said Eloi Mboso Kiamfu, a businessman, as he prepared to leave for Gisenyi, in neighboring Rwanda. "Goma almost does not exist any more."

Since the eruption began before dawn Tuesday, tens of thousands of residents in the region fled to Gisenyi. Some who tried to return Friday fled again as fires sent out a pall of smoke, the ground shook from aftershocks and the volcano continued to spit out ash and gas.

"This is terrible, my children have all disappeared, and I am confused and shocked," said Mulili Flaha, who fled Goma for Gisenyi on Thursday night when a dark, thick layer of lava approached her house. Her husband and five children all ran in different directions.

Swaths of lava as much as 200 feet wide had cut Goma in half, said Peter Hornsby, a logistics officer with MONUC, the U.N. peacekeeping mission to Congo.

Fire destroyed many of Goma's buildings, and explosions were set off as molten lava came into contact with gasoline and kerosene that residents had stored in plastic containers.

Looters and armed robbers in Goma made off with electronic equipment and other goods in shops before the lava got to them. Some looters were reportedly shot.

"There have been strong aftershocks every five minutes lasting for around 10 seconds," Elizabeth Byrs, spokeswoman at the U.N. Office for the Coordination of Humanitarian Affairs in Geneva, said Friday.

"Our people in the field said there was a huge explosion Friday morning, and that the volcano was pouring gas and ash," Byrs said, apparently referring to the fuel depot blast.

She said she could not discuss a casualty figure because staffers were still trying to get access to the affected areas.

"We're worried about the effects of a possible explosion under Lake Kivu, and possible contamination of the lake by the volcano," Byrs said.

Brian Baptie, a volcano seismologist at the British Geological Survey in Edinburgh, suggested casualties may not be as high as feared because the area's geography may have given residents time to flee the lava flow.

"Although the lava moves quite fast going down the flanks, once on flat land it moves quite slowly so people can get out of the way if they have warning," he said.

A Rwandan official, who requested anonymity, said as many as 500,000 people may have crossed the border to Gisenyi and the government was working with the Red Cross and the U.N. refugee agency to help them.

The U.N. peacekeeping mission in Congo, MONUC, evacuated 350 U.N. international staff members, U.N. spokesman Fred Eckhard said Thursday in New York.

Rwandan-backed rebels control Goma and the surrounding region. The United Nations has sent several thousand military observers and peacekeepers into Congo following a cease-fire in the civil war, which started in Goma in 1998.

MONUC's deputy commander, Gen. Roberto Martinelli, was to visit Gisenyi and Goma on Saturday, said a MONUC official who evacuated civilian and military staff from Goma to the Rwandan capital, Kigali.

Brenda Barton, spokeswoman for the World Food Program in Nairobi, Kenya, said the U.N. agency had earmarked 200 tons of food to help those displaced by the eruption and would bring in more.

The 11,381-foot Nyiragongo is on the western end of the Virunga chain of eight volcanoes stretching eastward into Rwanda. It last erupted in 1977.