[en] A search for a resonant state coupled to an electron-quark pair has been performed using collisions of the electron beam of 26.7 GeV and the proton beam of 820 GeV. With the integrated luminosity of 26.6 ± 1.6 nb^-1, scalar and vector leptoquarks have been searched for in the neutral current and charged current samples. The selected events agreed well with the prediction of the Standard Model, and no evidence has been found for production of leptoquarks decaying into e^- + jet or ν + jet. Limits on the coupling strength of scalar (vector) leptoquarks to electron and quark have been determined for masses from 50 (40) GeV to 225 GeV. A limit on the leptoquark mass has been also obtained at the 95% confidence level assuming that either left-handed or right-handed coupling exists to the electron-quark pair with electroweak strength. The mass limit depends on the cross section determined by the choice of quantum numbers. Leptoquarks are ruled out for masses below 216 GeV with the largest cross section and below 105 GeV with the smallest cross section. (author) 102 refs