  A search is described for the neutral Higgs bosons h^0 and A^0 predicted by
models with two scalar field doublets and, in particular, the Minimal
Supersymmetric Standard Model (MSSM). The search in the Z^0 h^0 and h^0 A^0
production channels is based on data corresponding to an integrated luminosity
of 25 pb^{-1} from e^+e^- collisions at centre-of-mass energies between 130 and
172 GeV collected with the OPAL detector at LEP. The observation of a number of
candidates consistent with Standard Model background expectations is used in
combination with earlier results from data collected at the Z^0 resonance to
set limits on m_h and m_A in general models with two scalar field doublets and
in the MSSM. For example, in the MSSM, for tan(beta) > 1, minimal and maximal
scalar top quark mixing and soft SUSY-breaking masses of 1 TeV, the 95%
confidence level limits m_h > 59.0 GeV and m_A > 59.5 GeV are obtained. For the
first time, the MSSM parameter space is explored in a detailed scan.
