Police are investigating after a suspected drug overdose left three men dead and four others in hospital - all of whom were wearing orange wristbands.

Five victims were found in an apartment on Pittsburgh’s South Side early on Sunday morning, another was found in an elevator outside the flat, and the final victim was discovered on a street corner nearby.

The conditions of those taken to hospital range from serious to critical.

Pittsburgh director of public safety Wendell Hissrich said the victims are all believed to be middle-aged men.

Authorities say they don’t believe there was a party at the building, which suggests the victims had arrived there after a night out.

The wristbands have become a key line of inquiry. Police have identified two concert and party venues that use orange wristbands, but have so far declined to name them.

Officials said they do not believe tainted drugs were distributed in large volume with the potential to harm others.