At least five people have died in a mass shooting in a Pittsburgh, Pennsylvania suburb. Six more are reported to be injured in the late-night shooting.

A police report says officers were responding to a 911 call in the suburb of Wilkinsburg at about 11pm on Wednesday. When they arrived they saw four people dead on the porch of a home where a party was being held.

Four more people were found wounded and taken to hospitals. Of those, one female died at the hospital, two more were reported in critical condition and another female was declared stable.

Neighbors have told KDKA they heard no fewer than 25 gun shots, and saw dozens of shell casings lying about the street afterwards.

Conflicting reports indicated a gunman was in police custody by midnight, but later information revealed the police are still searching for two suspects.

The ballistics report indicates there were two firearms shot by two separate assailants who carried out a surprise attack on the party being held in the backyard.

An investigation is underway.