An Adani Group company moved the Bombay High Court on Tuesday to seek to quash all requests by India to other countries for help in investigation against some group firms, The Indian Express reported.

Singapore’s High Court had recently upheld a lower court’s order to some group companies to produce documents in an investigation after receiving a letter rogatory from India. Letters rogatory are formal requests to foreign countries to seek judicial help in investigating offshore entities.

In its writ petition against the Union of India on Tuesday, Adani Enterprises Limited sought the quashing of all letters rogatory issued by the Directorate of Revenue Intelligence in connection with the investigation into alleged overvaluation of Indonesian coal imports.

The order by the High Court of Singapore was in the case of a petition filed by Adani Global Private Limited, which had sought a stay on a lower court’s order to Adani group firms to produce documents in a related case.

The Directorate of Revenue Intelligence is investigating at least 40 companies, including those from the Adani Group, Anil Dhirubhai Ambani Group, and Essar Group for alleged overvaluation of coal imports from Indonesia between 2011 and 2015.

In March 2016, the Directorate of Revenue Intelligence had alleged that Indonesian coal was imported directly to India but import invoices were routed through intermediaries – allegedly subsidiaries of Indian companies – in other countries to artificially inflate the value.

In 2016, three state-owned banks cited confidentiality norms and refused to provide information to the Directorate of Revenue Intelligence on transactions connected to the coal imports case made by leading power companies. The DRI had then written to foreign branches of the banks seeking information on transactions connected to the case.