ST. PAUL — Minnesota Gov. Mark Dayton was taken to a hospital for testing after fainting Sunday during an event in the Twin Cities suburb of Woodbury, his chief of staff said.

Jaime Tincher said in a statement that Dayton felt “increased pressure in his lower back” while speaking at the volunteer recognition event, which the statement described as “very crowded and hot.” He fainted and was taken to Regions Hospital “for further testing,” Tincher said.

The 69-year-old was to remain in the hospital overnight as a precaution.

The governor “is resting comfortably and joking with family, doctors, and staff,” Tincher said.

Bob Hume, a senior adviser to Dayton, told the Star Tribune and Pioneer Press the most likely culprit was dehydration.

The Democratic governor has had health troubles since taking office in 2011. He underwent elective lower back surgery in December at the Mayo Clinic in Rochester. His office said at the time that the procedure was similar to one he had three years earlier, which fused two vertebrae in his lower back.

He also had hip surgery in 2014 to alleviate chronic pain.