Indonesia's food and drug agency said on Monday it had revoked licences for syrup-type drug production by two local firms for violating manufacturing rules, as it investigates the deaths of more than 150 children due to acute kidney injury (AKI).

The decision by the BPOM agency came after Indonesia temporarily banned sales of some syrup-based medications and identified the presence in some products of ethylene glycol and diethylene glycol as possible factors in the AKI deaths, most of which were of children under five.

The two ingredients are used in antifreeze and brake fluids and other industrial applications but also as a cheaper alternative in some pharmaceutical products to glycerine, a solvent or thickening agent in many cough syrups. Ethylene glycol and diethylene glycol can be toxic and lead to AKI.

BPOM chief Penny K. Lukito told reporters the "oral liquid" manufacturing licences of the two companies, PT Yarindo Farmatama and PT Universal Pharmaceutical Industries, had been revoked, adding BPOM was pursuing criminal action against them.

Penny said the two firms produced drugs with substandard raw materials, failed to report a change in ingredients and used some materials in excess of guidelines.

PT Yarindo Farmatama in a statement denied using substandard raw materials in their products and said BPOM approved changes in their ingredients in 2020 and that there were no problems with its distributor.

A lawyer with PT Universal Pharmaceutical Industries declined to comment, citing the ongoing investigation.

Indonesia has seen a surge in AKI cases among children since August, which its health minister said was most likely due to changes in the raw ingredients used in cough and fever syrups.

Indonesia imports its raw ingredients for medicine mostly from China and India, according to the health ministry.

Indonesian health authorities said solvents used in the syrups from the two companies contained impurities.

BPOM said on Monday one of these solvents, propylene glycol, was made by Dow Chemical Thailand.

Dow Chemical Thailand said in a statement that "none of the suppliers mentioned by BPOM are our customers", and that its product does not contain ethylene glycol or diethylene glycol. It said it had submitted analytical data to the BPOM.

BPOM said it would look into distributors of the two drug makers to see if they supplied materials to other pharmaceutical firms.

Indonesia has been investigating AKI cases in consultation with the World Health Organization (WHO) after a similar incident in Gambia earlier this year, which has seen at least 70 deaths related to syrup medications made by India's Maiden Pharmaceuticals.