Six United States military planes arrived in the epicenter of the Ebola outbreak Thursday carrying more Marines who will be among the thousands of service people the U.S. says will be deployed to help fight the widening epidemic. The planes landed outside the Liberian capital, Monrovia, carrying 100 Marines who bring to just over 300 the number of American troops in the country. Vehicles unloaded boxes of equipment as the Marines formed a line on the tarmac and had their temperatures checked. The American military is working to build medical centers in Liberia and may send up to 4,000 troops to help with the crisis. The outbreak has killed more than 3,800 people so far, a preponderance of them in Liberia.