( CNN ) -- The ruptured Macondo well , a mile under the Gulf of Mexico off the Louisiana coast , has been pronounced dead following the worst oil disaster in U.S. history , but that does n't mean work associated with the spill is complete , the government 's point man for the disaster response said Monday . `` It 's going to go on as long as it takes to get the marshes and the beaches clean , '' retired Adm. Thad Allen told CNN 's `` American Morning . `` We have detailed plans that we 've negotiated with the states and the parishes in Louisiana to determine , if you will , how clean is clean . '' In some areas , such as Louisiana 's Barataria Bay , `` we 're going to stay with this for quite a while , '' he said . At some point , officials may decide they have done all they can , `` but for right now , we 're still at it . '' Although authorities say testing does not show high levels of oil remaining in the water , some researchers insist the oil has settled to the sea floor and infiltrated the bottom , where it could affect ecosystems . Asked about those reports , Allen said , `` I do n't think we can know too much about the Gulf of Mexico and the presence of hydrocarbons in the water column . '' He said he has been working with Jane Lubchenco , administrator of the National Oceanic and Atmospheric Administration , to develop a long-term subsea oil monitoring program that can be used not only in the response effort , but also as part of long-term restoration . `` What we really need to do is harness all the resources of the federal government and the state and local institutions , including academia , and build a database that can tell us more about the Gulf , '' he sad . `` Right now the readings we 're taking do n't show large concentrations . We 're really talking about microscopic particles of oil . We really need to understand better what 's happening on the sea floor . '' A joint investigative team is still probing the cause of the explosion on the Deepwater Horizon rig April 20 , which killed 11 men and triggered the underwater oil gusher . Crews last week , as part of the kill process , drilled into the annulus , or the outer ring of the well . No oil was found there , which could be an important clue in the investigation . Allen said it will be up to the joint investigative team , which includes the Department of Interior and others , to determine what occurred . `` There are a lot of theories , '' he said . `` ... A lot of people would tell you further down in the well , there was some kind of a crossover between the annulus and the casing pipe where it was cemented . I 'm sure we 're not going to know that until the investigative team has finished its work . '' BP , which owns the well , has left open the possibility of tapping back into the reservoir . Asked whether they should , Allen said that would be a policy decision between BP and the Department of Interior . `` Frankly , it 's above my pay grade , '' he said . But he added that any decision would involve `` a high level of assurance '' by the government . Asked his personal opinion , Allen said , `` I think we 've got a lot of problems with energy in this country related to fossil fuels and the need to move to other types of fuels . '' He called for a `` very balanced discussion '' taking the risks into account , as well as the need to have an energy policy as the transition is made to more environmentally friendly energy sources .
The response is ` ` go on as long as it takes , '' Thad Allen says . Allen says we need to better understand what 's happening on the sea floor . Whether BP re - uses the water should be a policy issue , he says .