Photo/Illutration Smoke is seen near a door of the Hayabusa No. 52 train on the Tohoku Shinkansen Line at JR Sendai Station on Oct. 9. (Provided by a source)

SENDAI—Police plan to investigate a man who accidentally leaked a chemical that burned three passengers and himself and sickened two others on a Tohoku Shinkansen train.

The chemical, believed to be used for geological surveys, apparently spilled from a plastic bottle on the Hayabusa No. 52 train running from Shin-Aomori Station in Aomori to Tokyo on Oct. 9, police said.

Investigators will determine if such a carrying method was appropriate for the chemical and whether the man can be charged with professional negligence resulting in injuries, sources said.

All four burn victims suffered slight injuries. Two others, including a railway worker, complained of feeling sick after inhaling vapor from the chemical.

Shortly before the bullet train stopped at Sendai Station, a passenger told the man, who is from Tokyo and in his 40s, that something was leaking from a black bag placed at his feet.

The man carried the bag toward one end of the car, but the chemical spilled out over the floor and caused burns to his feet.

One passenger told The Asahi Shimbun that a man told him outside the seating area that a sulfuric acid reagent had exploded by mistake. The bottoms of the man’s pants were damaged.

Another said she smelled a faint pungent odor.

A 5-year-old boy slipped on the chemical and fell to the floor while walking to a restroom. He suffered burns to his buttocks.

His parents burned their hands and feet when they tried to help him.

Smoke was rising from a bag placed near a door of the No. 7 car, according to a man who was waiting for the train on the platform.

Passengers in nearby cars were tense, not knowing what had happened.

Police officers and firefighters were called to the scene, and fire engines and ambulances were assembled outside Sendai Station.

The Hayabusa No. 52 was suspended, and all passengers had to disembark at the station, according to East Japan Railway Co.

Twelve Tokyo-bound trains on the Tohoku Shinkansen Line were delayed by up to 55 minutes, affecting about 7,300 passengers.