The five Americans being held in Nigeria remain in captivity despite assurances by their captors of their release today. The Americans are being held in the oil-rich Niger Delta region by two different militant groups. One American, John Stapleton (pictured), has been held for four weeks by the group MEND (Movement for the Emancipation of the Niger Delta) after being captured during a raid on a Chevron facility. In an e-mail last week to the Blotter on ABCNews.com, the group’s leader, Jomo, promised that Stapleton, along with five other foreign oil workers from Italy and Croatia, would be released May 30 in order to "spite the outgoing [Nigerian] administration," which left office yesterday. THE BLOTTER RECOMMENDS Webcast Hostages for Sale? Photos What’s Leading to Terror in the Niger Delta? Blotter Missing: 27 U.S. Citizens; Hopes Dim for Many, Some Held for Years Blotter First Photo of American Hostage From Nigerian Militant Group Click Here to Check Out Brian Ross Slideshows When asked yesterday by e-mail whether MEND still planned to release the hostages by today, Jomo answered "Definately [sic]." But as of six o’clock tonight in Nigeria, there’s been no word on their release. The four other Americans are being held by a militant Nigerian political group that calls itself the Niger Delta Freedom Fighters, also known as "Egbema One." The men, employees of Global Industries, a Nigerian-based oil servicing company that works with Chevron, were captured three weeks ago. Egbema One has told Nigerian media they plan an imminent release for the hostages but so far have refused to do so. The hostages — Mike Roussel, Chris Gay, Larry Plake and Kevin Faller — are reportedly in good health, but the kidnappers are demanding more political clout for their tribe and better sharing of oil revenue before they release the men. Do you have a tip for Brian Ross and the Investigative Team?