Nilton Dasilva, a church group leader from Northfield, Illinois, said he decided to take a detour during a group trip to a nearby coffee plantation and try to get as close as safely possible to the volcano.
"Now that we know it erupted, we're going to try to stop on the way and maybe take some pictures," Dasilva said.
Emergency workers reported that many villagers living around the slopes of the volcano had begun returning home. The Red Cross of Guatemala was winding down operations, coordinator Sergio de Leon said.
Guatemalan authorities ordered the evacuation of more than 33,000 of the 62,000 people living immediately around the volcano, many in isolated indigenous villages. Local media reported about 5,000 had left, and De Leon said many people had moved to the homes of friends or relatives a little farther away from the volcano.
Gustavo Chicna, a volcanologist with the national weather, earthquake and volcanology institute, said that the Volcano of Fire, Guatemala's most active, appeared to be in the final stages of its biggest eruption since 1974, when it exploded in an eruption five times more powerful than this week's.
Villagers and farmers living at the foot of the volcano were awoken Thursday by a massive roar during a series of eruptions that darkened the skies and covered surrounding sugar cane fields with ash.
"It thundered and then it got dark as the ash began falling," said Miriam Curumaco, a 28-year-old homemaker from the village of Morelia who had evacuated along with 16 family members to a makeshift shelter at a nearby elementary school. "It sounded like a pressure cooker that wouldn't stop."
The Volcano of Fire spewed rivers of bright orange lava down its flanks, prompting authorities to order evacuations in 17 nearby communities.
Hundreds of cars, trucks and buses, blanketed with charcoal gray ash, drove away from the volcano, which sits about six miles (16 kilometers) southwest of Antigua, toward Guatemala City. Thick clouds of ash reduced visibility to less than 10 feet in some areas. The elderly, women and children were evacuated in old school buses and ambulances.
Authorities set up a shelter at an elementary school in Santa Lucia, the town closest to the volcano, and by Thursday night some 750 people had arrived. Most were women and children carrying blankets.
Guatemala's emergency agency said lava rolled nearly 2,000 feet down slopes around the 12,346-foot-high Volcano of Fire.
Chicna said streams of extremely hot gas were also rolling down the sides of the volcano.
Guatemala's aviation administration said it had suspended all flights from the southern Mexican city of Tapachula to Guatemala City due to the ash.
By Thursday evening, the ash plume had decreased to a little more than a mile high, partly due to heavy rain, which diminished the potential risk to aviation, said Jorge Giron, a government volcanologist. But he said ash continued to fall heavily, and advised residents near the volcano but outside evacuation zones to clean their water systems before using them, and to not leave their homes because of the ash.