Two people are dead, and nine others have been injured in a Memorial Day mass shooting in Philadelphia, authorities said.

       The shooting took place at Fairmount Park in Philadelphia on Monday evening, the final day of the long Memorial Day weekend, when gunfire erupted at approximately 10:27 p.m. on Lemon Hill Drive at Poplar Drive, according to the Philadelphia Police Department.

       Two people – an unnamed adult man and woman -- were killed and at least nine others were injured in the shooting, including three teenagers between the ages of 15 and 17, Philadelphia Police Commissioner Kevin Bethel said.

       Multiple rounds were fired, Bethel said, and investigators are working to determine if several different weapons were involved.

       No one is in custody, Bethel confirmed, and no weapons have been recovered.

       Fairmount Park was busy during the day, according to ABC News’ Philadelphia station WPVI, as families and members of the community gathered for Memorial Day cookouts and barbecues.

       The names of the victims have not been released.

       This is a developing story. Please check back for updates.