The incident was reported around 6:45 a.m., city spokesman Dan Beerman said. Neither Clarke nor Beerman gave further details.
The NFL team’s new arena, called Levi’s Stadium, is expected to open in 2014. In a written statement on the fatality, the 49ers said the team is “deeply saddened.”
“Our thoughts and prayers are with the family, friends and co-workers affected by this tragedy,” the team said. “The 49ers family has lost a teammate today.”
Santa Clara is about 35 miles southeast of San Francisco.