Hundreds of people were evacuated from residences at the 9th Square apartment building in New Haven as the New Haven Fire Department investigated a gas odor.
Officials said a valve was left open at a nearby restaurant.
There are 188 units in the apartment building and residents were evacuated around 9 a.m. The evacuation lasted for about two hours.
The streets surrounding the building, located at 44 Orange St., were blocked off for the investigation.