TOKYO | 
 
 TOKYO (Reuters) - A strong earthquake hit Japan's southern island of Okinawa early on Saturday and Japan's weather agency issued a tsunami warning for up to 2 meters, but this was later lifted and there were no reports of major damage. 
 
 The U.S. Geological Survey said the 7.3 magnitude quake struck at 5:31 a.m. on Saturday (2031 GMT on Friday) 52 miles east of the island's capital of Naha, a city of about 320,000 about 1,600 km (1,000 miles) south of Tokyo. 
 
 The Japan Meteorological Agency, which put the magnitude at 6.9, warned residents near the coast to evacuate to high ground, but the tsunami warning was later lifted. 
 
 Okinawa prefectural police official Noritomi Kikuzato told Reuters there were no reports of injuries or major damage. 
 
 "First there was a strong vertical shake, then sideways. The strong quake lasted for about 10 seconds," said Naha city official Seiboku Sueyoshi. 
 
 An official at oil refiner Nansei Sekiyu KK said operations at its 100,000 barrels per day Nishihara refinery on the island were continuing normally after the quake and that there had been no reports of major damage to the facilities. 
 
 Public broadcaster NHK said local fire departments so far had no reports of injuries or damage to buildings. 
 
 Earthquakes are common in Japan, one of the world's most seismically active areas. The country accounts for about 20 percent of the world's earthquakes of magnitude 6 or greater. 
 
 In October 2004, an earthquake with a magnitude of 6.8 struck the Niigata region in northern Japan, killing 65 people and injuring more than 3,000. 
 
 That was the deadliest quake since a magnitude 7.3 tremor hit the city of Kobe in 1995, killing more than 6,400. 
 
 (Reporting by Yoko Kubota, Chris Gallagher, Edwina Gibbs and Osamu Tsukimori; Writing by Linda Sieg; Editing by Charles Dick) ||||| (CNN) -- A tsunami advisory announced shortly after a 7.0-magnitude earthquake struck Japan's Ryukyu Islands early Saturday has been canceled, Japan's Meteorological Agency reported. 
 
 There was no tsunami damage "though there may be slight sea level changes from now on," it said, referring to the areas affected by the advisory -- the Okinawa Islands, the Amami Islands and the Tokara Islands. 
 
 The quake was centered 10 kilometers (6.2 miles) deep and struck at 5:31 a.m. (3:31 p.m. ET Friday) about 85 kilometers (53 miles) from Okinawa. 
 
 The quake was felt on Okinawa, with shaking that lasted about 15 seconds, said Lt. Col. Daniel King of the U.S. Pacific Command. He told CNN that commanders in Japan and Hawaii were trying to get damage and casualty reports from U.S. military stations on Okinawa, but had heard nothing in the immediate aftermath. 
 
 About 20,000 U.S. troops -- mostly Marines, along with Navy and Air Force personnel -- are stationed on eight bases on Okinawa, he said. 
 
 Are you there? Send photos, video 
 
 iReporter Kristina Donaldson, who lives in central Okinawa, said the quake "seemed to last longer than other ones we have experienced here." 
 
 "We felt the quake pretty good this morning," she said, but life there was largely unaffected. 
 
 "I just walked down to the coastline and the kids are walking to school as they always do. No sirens, or any destruction from where we are." 
 
 Okinawa resident Eric Shepherd said his grandmother-in-law described it as the strongest quake she had felt in her 90 years on the island. 
 
 "It felt like some really bad airplane turbulence," Shepherd said, adding that one of his two children slept through what seemed like a minute-long "rumble." 
 
 "I had no problem walking to the kids' room to check on them" during the quake, he said. 
 
 CNN's Mike Mount contributed to this report. ||||| A strange sea of bubbles filled streets in a southern Japanese city in the early hours of Saturday morning, after an earthquake and several aftershocks rattled the south of the country. 
 
 In the Tenjin area of Fukuoka city, motorists and pedestrians made their way through the foamy mess after it spilled out onto the streets. 
 
 Some reported that an underground pipe burst, releasing the material, but little information was immediately available. 
 
 SEE ALSO: Powerful earthquake rattles southern Japan 
 
 An earthquake rattled the area shortly before the foam appeared in the street, leading many to believe the weird white substance was linked to the quakes. 
 
 Residents of Tenjin shared images of the foamy stuff on Twitter, but most seemed baffled about what the substance could be. 
 
 A powerful earthquake with a preliminary magnitude of 7.3 struck southern Japan early Saturday, barely 24 hours after a smaller quake hit the same region and killed nine people. 
 
 While it was not immediately clear whether the latest quake increased the death toll, Japanese broadcaster NHK said a number of calls were coming in from residents reporting people were trapped inside houses and buildings. Video showed a resident, apparently rescued from underneath a collapsed house, on a stretcher being taken to a hospital by ambulance. 
 
 The quake shook the Kumamoto region at 1:25 a.m. Saturday, and several aftershocks soon followed. Japan's Meteorological Agency issued an advisory for a tsunami up to 1 meter (3 feet) high along the coast west of the epicenter in Kumamoto; the advisory was lifted less than an hour later. 
 
 Sirens of patrol vehicles were heard in the background as NHK reported from the hardest-hit town of Mashiki. The asphalt outside the town hall had a new crack, apparently made by the latest earthquake. 
 
 The Nuclear Regulation Authority said no abnormalities were found at the Sendai nuclear plant, where the only two of Japan's 43 operable reactors are online. NHK video showed that stones tumbled from the walls of historic Kumamoto Castle, and a wooden structure in the complex was smashed, adding to damage from Thursday at the site. 
 
 At the Ark Hotel, east of the castle, hotel guests woke up to strong shaking and a warning siren. Hotel staff asked guests, including tourists and journalists covering the quake, to evacuate their rooms and gather in the lobby for safety. 
 
 Thursday's weaker, magnitude 6.5 earthquake brought down buildings and injured about 800 people, in addition to killing nine. The epicenter of Saturday's earthquake was about 12 kilometers (8 miles) northwest of Thursday's, and at a depth of about 10 kilometers (6 miles), Saturday's quake was shallower. 
 
 Additional information from the Associated Press. 
 
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– A tsunami warning has been lifted and residents of Okinawa are breathing a sigh of relief after an earthquake rattled the southern Japanese island early Saturday morning. " First there was a strong vertical shake, then sideways," an official of the city of Naha tells Reuters. "The strong quake lasted for about 10 seconds ." There were no immediate reports of damage or casualties on the eight American military bases in the area, CNN reports.