(@andreamsaul/Twitter)

LAS VEGAS - Ann Romney's plane made an emergency landing today in Colorado after smoke filled the cabin because of an apparent electrical fire.

Romney, wife of the Republican presidential nominee, Mitt Romney, was not harmed in the incident, spokeswoman Sarah Haley said.

Haley tweeted following the incident, "Don't need any caffeine to wake me up now! #adventure "

"A HUGE thank you to the crew and first responders for keeping us safe today!" she wrote.

The flight was heading from Omaha, Neb., where Mrs. Romney had attended fundraisers this afternoon, to Santa Monica, Calif.

In a recorded conversation between the plane and Denver International Airport's flight tower, a man's voice could be heard saying, "We have an electrical issue here and we're going to declare an emergency."

"We'll probably need assistance here," he said. "We got smoke in the cabin."

Haley said the plane, a Canadair Challenger 600 regional jet, was surrounded by fire trucks when it landed at the Denver International Airport.

No media travels with Ann Romney on her flights, but she was accompanied by four staffers, including Haley, two U.S. Secret Service agents, and three crew members.

Romney and the other passengers were instructed to put their seat belts on during the emergency landing.

The FAA said in a statement said that a Canadair regional jet charter flight operated by World Wide Jet diverted to Denver today at about 2:40 p.m. MDT after the pilot reported smoke in the cockpit.

The aircraft landed safely on runway 35L and passengers exited the aircraft via stairs on a taxiway, according to the FAA.

The flight was at 40,000 feet when it turned around to make the emergency landing, according to Flight Aware.

Romney campaign spokeswoman Andrea Saul tweeted a photo from the scene, showing firefighters storming onto the plane after it landed.

Saul said that Mitt Romney spoke with his wife as soon as she was safely on the ground in Denver.

The Denver Fire Department, the Denver Police Department and Airport Operations responded to the call.

ABC News' Lisa Stark and Matt Hosford contributed to this report.