(CNN) -- Phone service went out at Democratic and Republican field offices in New Hampshire Monday, the day before midterm elections, party officials said.
A spike in campaign robocalls may be the culprit, according to Comcast, one of the telephone services in the area.
"Comcast -- and we believe, other local phone carriers in New Hampshire and Massachusetts -- are experiencing severe call volumes on the evening before the election due to auto dialing activity that is generating a massive number of inbound political phone calls to our network," company spokesman Marc Goodman said.
Democratic Party officials said they alerted the New Hampshire Attorney General's Office after volunteers at 11 field offices reported they were unable to make calls starting at 1:30 p.m. Monday.
"Considering the crimes committed by the state Republican Party in past elections, unfortunately we felt the need to contact the authorities so they can be aware of the situation," New Hampshire Democratic Party Chair Raymond Buckley said in a statement.
New Hampshire Republicans also lost phone service in six offices, party spokesman Ryan Williams said.
"We are using our backup phones to make calls. The Democrats know they will be beaten. They are going to lose. They are just making things up to deflect from the coming losses," he said.
A former New England regional director of the Republican National Committee was convicted in 2005 for his role in an operation to jam Democratic phone banks in a 2002 New Hampshire election. A federal judge sentenced James Tobin to 10 months in prison for his involvement in setting up the scheme, which involved placing repeated hang-up calls to the New Hampshire Democratic Party to jam the opposition's phone lines.
Additionally, a former New Hampshire Republican official, a businessman and the head of a telemarketing firm pleaded guilty to playing roles in the operation.
Comcast is trying to determine who owns the telephone numbers placing the robocalls, Goodman said.
"As soon as we were made aware of the congestion this was causing, we began to re-route traffic around it," he said.