SAN MATEO (CBS SF) — A coding problem affected about 140 electronic voting machines throughout San Mateo County this morning, but the issue was resolved in about 90 minutes, according to a county election official.

The problem was identified at about 7 a.m. — an hour before polls opened for Election Day — on some Hart InterCivic “eSlate” machines used by the county, assistant chief elections officer Jim Irizarry said.

READ MORE: EDD Fraud: Fresno Man, Central Valley Inmate Plead Guilty To $103K Unemployment Benefit Scheme

The issue was with passcodes that connected individual machines to the central processing unit at election headquarters in San Mateo, Irizarry said.

READ MORE: 47YO Woman Killed After Stopping On I-80 Near Crash

The issue was resolved by 8:30 a.m. and during the time the electronic machines were down, people were still able to vote via paper ballots, he said.

MORE NEWS: San Mateo Police Arrest 2 In Connection With Multiple Robberies, Vehicle Thefts During Weekend Crime Spree

There were a few minor hardware issues later in the day but Irizarry said shortly before polls closed at 8 p.m. that overall “the rest of the day has gone relatively smoothly.”