Near the second order phase transition point, QCD with two flavours of massless quarks can be approximated by an O(4) model, where a symmetry breaking external field 𝐻 can be added to play the role of quark mass. The Lee-Yang theorem states that the equation of state in this model has a branch cut along the imaginary 𝐻 axis for |𝐼𝑚 [𝐻] | > 𝐻 𝑐 , where 𝐻 𝑐 indicates a second order critical point. This point, known as Lee-Yang edge singularity, is of importance to the thermodynamics of the system. We report here on ongoing work to determine the location of 𝐻 𝑐 via complex Langevin simulations.