Around 10-15 students are still admitted in the Humdard Institute as a precautionary measure and are likely to be discharged today, a senior police officer said.
The police are sending notices to the companies involved in the transportation of the container, the customs department and the Container Corporation of India Ltd (CONCOR), the custodian of the depot.
"We have asked them to submit a list of the agreements and documents pertaining to the transportation of the container and its content," he said.
The officer said their probe will focus on ascertaining where the carelessness occurred and the agency responsible for it.
Yesterday, police had said it is suspected that the leakage might have happened due to the containers not being properly sealed after being checked.
Classes at the two schools that were affected by the incident remained suspended yesterday.
Meanwhile, the National Green Tribunal has sought the responses of the Centre and the Delhi government. The green panel issued notices to the Ministry of Environment and Forest, the Delhi government, the Railway Board and the DPCC and asked them to file their replies within a week.
The NDRF had said a truck carrying 80 cans of chloromethyl pyridine had left the Tughlakabad depot for Sonepat at 3.30 am on Saturday.
The Delhi government, which ordered a magisterial probe into the incident, has issued a show cause notice to the depot authorities.
Police had registered an FIR in the matter under various sections of IPC and the Environment (Protection) Act against unidentified persons.
The southeast district administration also issued a show cause notice to the Customs department and the CONCOR.
Around 450 girl students were hospitalised on May 6 after toxic fumes spread due to chemical leakage at a container depot near two schools in southeast Delhi's Tughlaqabad area.
Get the latest election news, live updates and election schedule for Lok Sabha Elections 2019 on ndtv.com/elections. Like us on Facebook or follow us on Twitter and Instagram for updates from each of the 543 parliamentary seats for the 2019 Indian general elections.