Robo-calls on Tuesday that claimed the Democratic candidate won the gubernatorial election in Maryland hours before the polls had closed and advised voters to "relax" are now under investigation.

The call came from a 202 area code, the area code for Washington, DC. No records are listed for the number in phone databases.

"I'm calling to let everyone know that Governor O'Malley and President Obama have been successful," a woman's voice on the recording said. "Our goals have been met. Our polls were correct and we (unintelligible). We're OK. Relax. Everything is fine. The only thing left is to watch on TV tonight. Congratulations and thank you."

Polls in Maryland did not close until 8pm, but residents reported receiving the robo-calls around 6pm, according to the Baltimore Sun.

Doug Gansler, the Attorney General of Maryland, says he will investigate the robo-calls and prosecute illegal campaign tactics. The recording fails to identify who authorized the call, which is illegal in Maryland.

"Sadly, this is the kind of gutter politics that we have come to expect from Bob Ehrlich and the Republican Party," said Baltimore Mayor Stephanie Rawlings-Blake.

A spokesman for the O'Malley campaign also blamed the robo-calls on the Republican Party. (The incumbent governor ultimately won re-election.)

"It is unfortunate that they would do something like this," he said. "It has to be politically motivated."

The Maryland Republican Party denies having any involvement in the robo-calls.

"Whoever is responsible for its content should be prosecuted to the full extent of the law," Republican Party Chairwoman Audrey Scott said in a statement. Blaming the Republican Party for the calls "is absolutely irresponsible," she added.

Similar robo-calls were reported in Kansas, where Democrats alleged a pro-Republican group was confusing voters with automated telephone calls claiming the election occurs on Wednesday.

In South Carolina, a Republican campaign consultant faces six arrest warrants for making illegal robo-calls.

The State Law Enforcement Division say the calls were political in nature and did not properly disclose the identity of the party that authorized the call, WIS News reports.