Smoke due to a "minor mechanical issue" forced first lady Melania Trump's airplane to return to Andrews Air Force Base Wednesday morning while en route to an event in Philadelphia.

No injuries were reported and the plane landed safely at Andrews. The first lady then took another plane, arriving later in Philadelphia to meet at Thomas Jefferson University Hospital with families of children who were affected by exposure to opioids while in the womb.

"Minor mechanical issue, " Stephanie Grisham, the first lady's communications director, said in a statement about the first plane. "Everything is fine and everyone is safe."

The press pool on the flight reported that a "thin haze of smoke" appeared in the plane along with the smell of something burning.

Passengers were given wet towels to breathe through, the pool reported.

The first lady is expected to be accompanied by U.S. Health and Human Services Secretary Alex Azar during the visit to the hospital, which has provided care to mothers with opioid use disorder and their newborn children for more than 45 years.

She also plans to tour a neonatal intensive care nursery and speak at a U.S. health department conference on a new system that tracks infants suffering from opiate withdrawal.

The first lady's visit is one of the stops she's making to promote her "Be Best" campaign, which focuses on major issues affecting children, including the importance of healthy pregnancies.

This story contains information from the Associated Press.