Four people were rushed to a hospital early Sunday after inhaling fumes in a building in Tokyo's Shinjuku Ward.
The four -- three women aged between 19 and 27 and a man aged 41 -- were treated for throat irritation, but their injuries were not serious, police and firefighters said.
The incident occurred around 12:50 a.m. in the No. 21 Tokyo Building in Shinjuku's Kabukicho district, a popular nightspot. Some 35 people inside the building complained of throat irritation from the fumes, they said.
People on the seventh and 10th floors detected the fumes, which were strong enough to provoke coughing fits in some, they said.
Police and firefighters said they suspect the odor might have come from an old air conditioner. No toxic substances have been detected at the site.
The building, which houses restaurants and sex-related shops, is located near the building in which 44 people were killed in a fire in September.