First lady Melania Trump takes a seat during a visit to The Royal Hospital Chelsea in central London in July. Image Credit: AP

Washington: A plane carrying US First Lady Melania Trump was forced to turn back on Wednesday after smoke appeared in the cabin, journalists on the flight said.

She was on her way from Washington to Philadelphia when there was "a minor mechanical issue", according to her spokeswoman, Stephanie Grisham.

"Everything is fine and everyone is safe," Grisham said in a statement.

The airplane returned to Joint Base Andrews, an air force facility used by the White House outside Washington, DC.

CNN and other US networks said that reporters aboard the plane noticed smoke in the cabin and were told to hold wet towels over their faces if it got worse.

The smoke dissipated and the aircraft returned without further incident.

Trump was on her way to visit a Philadelphia hospital specialising in the treatment of mothers with opioid use disorders and babies born with addictions to drugs they were exposed to while still in the womb.