A US Navy warship carrying humanitarian aid anchored in the southern port of Batumi on Sunday, sending a strong signal of support to an embattled ally. In central Georgia, an oil train exploded and caught fire, sending plumes of black smoke into the air. A Georgian official said the train hit a land mine and blamed the explosion on Russian forces, who withdrew from the area Friday. The Russian Defense Ministry declined to comment, saying it was not clear what happened. The blast came amid persistent tensions in Georgia. Russia pulled the bulk of its troops and tanks from its small southern neighbor Friday after a brief but intense war, but built up its forces in and around two separatist regions and left other military posts deep inside Georgia. The guided missile destroyer USS McFaul, loaded with 72 pallets of humanitarian aid, is the first of five American ships scheduled to arrive this week. The much-needed aid and the damaged train were a stark reminder that it will take substantial amounts of aid and many months of rebuilding before Georgia can recover from the war with Russia. Five days of fighting damaged cities and towns across the country and displaced tens of thousands of Georgians. Outside Gori, an Associated Press reporter saw 12 tanker cars in a confused jumble, some askew on the railway line and others off the tracks, some lying on their sides. Firefighters were hosing down the wreckage and appeared to have the blaze under control. Georgian Interior Ministry spokesman Shota Utiashvili said the train hit a mine. He said there were no casualties, but that the blast had also set off explosions at an abandoned munitions dump nearby. The television report said two homes were damaged. Georgian Public Television, which showed massive clouds of billowing black smoke rising from the fire, reported at least 10 tanker cars were burning and another 20 had been uncoupled and pulled away to prevent the fire from spreading. Utiashvili blamed the incident on the Russians. Georgian officials say Russian forces deliberately damaged infrastructure before the pullback to weaken Georgia, and accused the Russians of blowing up a train bridge last week. Speaking at the site west of Gori, the director of Georgia's railways, Irakli Ezugbaia, agreed that the blast was probably caused by a mine. He said an investigation was under way and other mines had been found on the tracks. Georgian forces removed a large artillery shell that had been jammed under the tracks and covered with stones. Ezugbaia said the train was carrying crude oil from Kazakhstan that was being transported by an Azerbaijani company. It was headed to a Georgian Black Sea port. Georgia straddles a key westward route for oil from Azerbaijan and other Caspian Sea nations including Kazakhstan, giving it added strategic importance as the US and the European Union seek to decrease Russia's dominance of oil and gas exports from the former Soviet Union. The conflict between Russia and Georgia, a small ex-Soviet republic whose pro-Western leaders have tried to shed Moscow's influence and sought NATO membership, has brought Russian-US relations to a post-Cold War low. A US official said the American ship anchored in Batumi, Georgia's main oil port, which is close to the southern end of Georgia's Black Sea coast near Turkey, because of concerns about the Georgian port of Poti. Russian troops still hold positions near Poti, and reports from AP journalists in Poti have shown Russians looting the area. Georgian port officials have said radar, Coast Guard ships and other port facilities were extensively damaged by Russian troops. "Because there was damage to the port facility in Poti, we wanted to be sure the humanitarian aid got in," US Embassy spokesman Stephen Guice said in Batumi. At dockside in Batumi, with the McFaul anchored offshore, US Navy officials in crisp white uniforms were met Sunday by Georgian officials including Defense Minister David Kezerashvili and the regional governor. Local children gave the Americans wine and flowers. "It's highly important for us here to have representatives of the navy of our biggest friend, the US," Kezerashvili said. "This is a signal to the Russians, and the signal is: we are not alone. The world is with us." The commander of the five-ship US task force, Navy Capt. John Moore, downplayed the significance of a destroyer bringing aid. "We really are here on a humanitarian mission," he said. The McFaul, an Arleigh Burke-class destroyer, is also outfitted with an array of weaponry, including Tomahawk cruise missiles, which can carry either conventional or nuclear warheads, and a sophisticated radar system. For security reasons the Navy does not say if ships are carrying nuclear weapons, but they usually do not. The deputy chef of Russia's general staff suggested Saturday that the arrival of the McFaul and other NATO members ships would increase tensions in the Black Sea. Russia shares the sea with NATO members Turkey, Romania and Bulgaria as well as Georgia and Ukraine, another ex-Soviet whose pro-Western president also is leading a drive for NATRO membership. "I don't think such a buildup will foster the stabilization of the atmosphere in the region," Russia's ITAR-Tass news agency quoted Col. Gen. Anatoly Nogovitsyn as saying. An APTN cameraman and his Georgian driver were roughed up and briefly detained by Russian troops outside Poti on Sunday as he shot video of Russian positions outside the port. Soldiers damaged a videocamera and seized them, before turning them over to Georgian police, who released them. Hundreds of Georgians flocked back to Gori on Saturday, one day after the Russians withdrew, to begin the Herculean task of rebuilding their lives. Their homecoming was laced with despair, disbelief and anger. "Barbarians, that's what they are. They kill innocent people here ... how many kilometers outside the battlefield? They bombed all over Georgia," Zurab Gvarientashvili, a 31-year-old engineer, said as he viewed his apartment, destroyed by a Russian bomb. "And what for? So that innocent people suffer?" he asked. Gori is 30 kilometers south of the capital of the separatist region South Ossetia, where Georgian forces launched an assault on Aug. 7, sparking the war and an international crisis. Next to one bomb crater in another part of Gori, Merdiko Peredze's goats grazed on burnt grass as he showed off the shrapnel that landed next to his decrepit two-room home. Peredze said he was refugee twice over - once after fleeing his home amid fighting in the early 1990s in Abkhazia, a breakaway region like South Ossetia, and now again, with his house in tatters. "I'm an old man but I will return to Abkhazia," he vowed. "Russian, Georgians, Ossetians - we should all be living in peace together, like we did under Stalin."