Fire department officials said they received an emergency call shortly after 4:30 p.m. on May 10 that spray appears to have been discharged inside a train traveling through Kawasaki, Kanagawa Prefecture.

The train was heading toward Tokyo on the JR Tokaido Line.

A couple in their 30s and their 1-year-old daughter complained of symptoms such as sore throat and headache.

They were taken to hospital, but all were reported to have mild symptoms.

Officials said an inspection of the train stopped at JR Kawasaki Station found no irritating substances or toxins.

In addition, police could not find any signs of any spray being dispersed when they checked security camera footage.

As multiple passengers reported noticing a smell similar to pepper, police and fire department officials are investigating the circumstances further.