SAN MARCOS, Calif.—Authorities sought May 9 to determine who fired a gun near a San Marcos park as nighttime youth baseball games were underway there, sending at least one round whizzing harmlessly onto one of the occupied diamonds.

Several 911 callers reported hearing three to five gunshots near Mission Sports Park on Bailey Court at about 7:45 p.m. Monday, according to the San Diego County Sheriff’s Department.

Deputies, including the crew of a sheriff’s patrol helicopter, searched the area, finding a bullet on one of the fields where children had been playing baseball, Lt. Gavin Lanning said. The personnel located no victims or suspects, he said.

Administrators at nearby Palomar College put the campus on lockdown as a precaution during the search. The security measures were lifted at about 9:30 p.m., Lanning said,

No suspects or witnesses to the origin of the shooting had been located as of Tuesday afternoon, the lieutenant said.

About 200 people were in the park when the gunshots sounded, according to Lanning.