The World Health Organization on Monday said the risk to children from some contaminated batches of the oral polio vaccine is “minimal”, Reuters reported. This is because of the high routine polio immunisation coverage in India, spokesperson Shamila Sharma said.

Last month, surveillance reports had shown signs of the polio type II virus in stool samples of some children in Uttar Pradesh. The Union Ministry of Health and Family Welfare then ordered an investigation into claims of the presence of the virus in some batches of the vaccine manufactured by a company in Ghaziabad.

The presence of the virus has been confirmed in one batch of 50,000 vials, and it is suspected in two more batches of 1 lakh vials, an unidentified ministry official told PTI. Officials confirmed on Monday that some vials of the contaminated vaccine were given to children in Maharashtra and Telangana as well. The ministry has issued advisories to the three states to ensure that polio surveillance teams trace those children and keep a close watch on them for symptoms.

The polio type II virus strain has been eradicated across the world. India had ordered this type of vaccine to be discontinued in 2016. Children born after that do not have immunity against the type II virus, and are at a higher risk, reported The Times of India. Officials told Reuters they are investigating why and how the Ghaziabad company, Bio-Med Private Limited, was still producing such vaccines.

On Thursday, the Ghaziabad Police arrested SP Garg, the managing director of the firm, based on a complaint by the Central Drugs Standard Control Organisation. The Drugs Controller General of India has asked the firm to stop the manufacture, sale or distribution of the vaccine.

A testing of samples of the oral polio vaccine collected from the company between September 12 and 14 showed that they were adulterated and “not of standard quality”. Garg has denied the allegations and claimed his company was told to stop the sale of the vaccine “with no specific reason”.