Nine people were taken to hospital after a hazardous chemical was sprayed on a train platform in Tokyo on Wednesday, police said.

About 20 people complained about an unusual odor at about 5:40 p.m. on platform No. 3 at Takadanobaba Station on Seibu Railway Co.’s Shinjuku Line. Among them, nine reported sore throats and eyes, the police said.

The nine were taken to the hospital but their injuries were not serious, rescue workers said.

Some witnesses said a substance resembling paint thinner was sprayed, but rescue workers at the scene detected no trace of such a chemical.

The incident took place as commuters were traveling home after work. Trains were not affected, according to the railway operator.