The NATO base in Afghanistan is in the Balkh province, which is currently under the governorship of Ustad Atta Mohammed Noor, a Tajik ex-member of the Mujahadeen and commander of the Northern Alliance.
However, three issues should be addressed here:
1. The PRT (Provincial Reconstruction Team, which is the term used for NATO operations groups in Afghanistan broken down by province) in Balkh is headed by Sweden and is based in Mazar-i Sharif, with a relatively small number of American troops (less than 100). This means that there'd be a small number of potential suspects, and it also means that there'd be a degree of expected cooperation with the Swedish authorities in any investigations.
2. The head of the Provincial Council of Balkh, Farhad Azimi, has become increasingly critical of both Western NGOs and the PRTs, accusing them of corruption and ineptitude and demanding that they leave the region. He would likely use this incident as further proof of his charges, and so there could be quite a bit of local political pressure, despite the relative security of the province.
3. According to Mohammad Arif Nairan, a visiting scholar to the University of Montana who I recently heard lecture at the annual Central & SW Asian Conference, Governor Noor is one of the primary movers of opium to Uzbekistan & Tajikistan (through which it is shipped north to Russia). While this may seem contradictory as Noor has cracked down hard on opium production in his province, there are likely two reasons for this. First, he could be consolidating his power in the trade by eliminating local competition in production and distribution. Second, like the Taliban before him he could be artificially driving prices up by limiting the output of supply to Russia while continuing to export his own stock. Regardless, the trafficking of opium through the district will likely complicate matters further.