A Hungry Jack's restaurant in Adelaide's north-east had to be evacuated on Thursday night after staff and customers were affected by a substance "similar to pepper spray", police have said.
SA Police is now investigating the incident, which occurred at the fast food outlet at Ridgehaven about 8:00pm.
Patrols, paramedics and Metropolitan Fire Service (MFS) crews were called to the Hungry Jack's restaurant on North East Road after staff and customers began coughing and complaining of sore throats.
Police said the cause was initially thought to be a gas leak, but that was discounted by MFS crews at the scene.
"Staff and customers were affected by an unknown substance … and were treated at the scene by paramedics," police said in a statement.
"Further investigations revealed the substance was similar to pepper spray."
An MFS spokesperson said only a few people suffered from a cough, and that about 10 staff and patrons were assessed by the South Australian Ambulance Service (SAAS) "as a precaution".
"They got everyone out of the building, SAAS had a look at everyone and there were no issues with anybody," she said.
"[MFS] went and had a look at all the CCTV footage with the management and checked the whole place out and there was nothing.
"It might have been a kid pulling a prank or something, you just don't know."
Police have urged anyone with information to call Crime Stoppers on 1800 333 000.
