The New Hampshire Attorney General's Office has opened an investigation into whether presidential hopeful Mitt Romney's staff might have made an illegal traffic stop.

The investigation was opened Thursday, the same day a group of conservative activists with a connection to rival Sen. John McCain complained about the incident.

ConserveNH President Paul Nagy wrote a letter to Attorney General Kelly Ayotte asking her to check if Romney aides illegally stopped a New York Times reporter, checked his license plate against a database and overstepped their authority.

"We want attention to the indiscretion," said Nagy, who said he is not supporting a candidate. "I think there is a bunch of arrogance involved in this. We just don't do that to guests when they visit our state during the presidential primary season."

One of ConserveNH's founder, Patrick Hynes, works for McCain's political action committee, Straight Talk America.

Nagy said the letter was sent independently of the McCain campaign and said he was unaware that Hynes is on McCain's payroll.

McCain's New Hampshire spokeswoman Jill Hazelbaker denied any connection between the campaign and the letter.

"I can confirm that we were asked to look into the matter," said Jane Young, chief of the criminal justice bureau at the Attorney General's Office. "We are officially looking into the matter."

Romney's campaign on Wednesday denied a report that aides pulled over Times reporter Mark Leibovich, who was trailing the former Massachusetts governor's caravan in New Hampshire, checked his license plates and told him to leave.