JAKARTA, Indonesia -- A 7.7 earthquake shook Indonesia's northwest island of Sumatra early Wednesday, prompting a brief tsunami warning and sending residents rushing for higher ground. There were scattered reports of injuries, but only minor damage was reported in most areas.
The quake struck at 5:15 a.m. and was centered 125 miles northwest of the coastal town of Sibolga in Sumatra at a depth of 19 miles, the U.S. Geological Survey said. It had earlier said the quake measured 7.8.
Indonesia's Meteorology and Geophysics Agency and the Pacific Tsunami Warning Center in Honolulu issued tsunami warnings following the quake, but lifted them two hours later.
A hospital on Simeulue island off the coast of Sumatra admitted 17 people for treatment of injuries sustained in the quake, including four in critical condition, said Capt. Ajas Siagian, a deputy police chief for the area.
Abdul Karim, a government spokesman in Simeulue, said dozens of houses collapsed or were damaged in Teupah Selatan village. He said no larger buildings were reported damaged, but electricity had been knocked out on the island.
"We are still collecting reports of damages and injuries ... but the situation has returned to normal and people are going back home," he said.
Fauzi, a seismologist at the meteorology agency, said the quake would have "at least caused cracks in many buildings and houses, especially in areas closest to the epicenter."
"That's why we are still trying to get data of damage in some remote areas that remain difficult to reach due to lack of communication and blackout," said Fauzi, who goes by only one name.
Local network Metro TV reported that a dormitory for nurses partially collapsed in Aceh's Singkil district and one woman suffered minor injuries in the rush to get out of the building. It said fires sparked by the quake had burned at least 14 houses in Medan, the capital city of North Sumatra province.
At least five strong aftershocks measuring up to 5.2 were recorded, the meteorology agency said.
The quake, which struck as people in the region were preparing for morning prayers, caused panic in Medan, about 135 miles from the epicenter, and other cities in the region. Electricity was cut in Medan, Banda Aceh -- the provincial capital of Aceh -- and other areas.
People in several cities along the southeastern coast of Sumatra as well as Sinabang on Simeulue island and Gunung Sitoli on nearby Nias island poured into the streets and rushed to higher ground after the quake.
"Rumors about a tsunami panicked villagers living near the beach," said Eddy Effendi, a resident on Nias island. "They ran away on motorbikes and cars or by climbing the hills. There was panic and chaos everywhere, but I don't see serious damage or injuries in my village."
Residents in Sibolga said the shaking lasted more than a minute and utility poles in the area were knocked down.
The quake was felt as far away as the outskirts of Malaysia's Kuala Lumpur, about 320 miles away. There were no reports of damage there.
A 2004 tsunami triggered by a magnitude-9.2 earthquake in the same part of Indonesia killed 230,000 people in a dozen countries on the Indian Ocean basin.