The Topol missile was deployed at previously developed deployment sites. After the INF Treaty was signed in 1987 several SS-20 deployment sites were adapted to launch the Topol missiles. The United States expressed specific concerns during the INF treaty negotiations. When the SS-25 missile system was deployed in the field, with its missile inside the canister and mounted on the launcher, the US contended that the canister might conceal an RSD-10 Pioneer missile. This was of concern because unlike the single warhead of the RT-2PM Topol, the RSD-10 carried up to 3 warheads. A resolution was reached after the Soviet Union agreed to allow inspection parties to use radiation detection systems to measure fast neutron intensity flux emanating from the launch canister. A launch canister with a missile inside containing a single warhead, such as the RT-2PM Topol, emitted a different pattern of fast neutrons than did one with a missile having three warheads, such as the RSD-10.