  We describe a search for the pair production of first-generation scalar and
vector leptoquarks in the eejj and enujj channels by the D0 Collaboration. The
data are from the 1992--1996 ppbar run at sqrt{s} = 1.8 TeV at the Fermilab
Tevatron collider. We find no evidence for leptoquark production; in addition,
no kinematically interesting events are observed using relaxed selection
criteria. The results from the eejj and enujj channels are combined with those
from a previous D0 analysis of the nunujj channel to obtain 95% confidence
level (C.L.) upper limits on the leptoquark pair-production cross section as a
function of mass and of beta, the branching fraction to a charged lepton. These
limits are compared to next-to-leading-order theory to set 95% C.L. lower
limits on the mass of a first-generation scalar leptoquark of 225, 204, and 79
GeV/c^2 for beta=1, 1/2, and 0, respectively. For vector leptoquarks with gauge
(Yang-Mills) couplings, 95% C.L. lower limits of 345, 337, and 206 GeV/c^2 are
set on the mass for beta=1, 1/2, and 0, respectively. Mass limits for vector
leptoquarks are also set for anomalous vector couplings.
