Searches for scalar top and scalar bottom quarks, as well as for mass-degen
erate scalar quarks of the first two families are performed at 189 GeV cent
re-of-mass energy with the L3 detector at LEP, No signals are observed, Mod
el-independent limits on the scalar top production cross sections are deter
mined for the decay modes (t) over tilde(1) --> c<(chi)over tilde>(0)(1) an
d (t) over tilde(1) --> bl<(nu)over tilde>. For scalar quarks of the other
flavours (q) over tilde --> q<(chi)over tilde>(0)(1) decays are considered.
Within the framework; of the Minimal Supersymmetric Standard Model mass li
mits are set at 95% C.L. for these particles, Indirect limits on the gluino
mass are also derived. (C) 1999 Published by Elsevier Science B.V. All rig
hts reserved.