Daiichi Sankyo, which owns India's biggest drug maker, said it had formed a team with Ranbaxy Laboratories [Get Quote], to address the data 'falsification' charges levied by the US Food and Drug Administration even as analysts foresaw more trouble for the drug maker.

Ranbaxy and Daiichi' shares plunged the most in more than four months on speculation of possible withdrawal of approved Abbreviated New Drug Approvals from the Himachal Pradesh facility and on concern that other drug regulators may review their stand on the facility.

The USFDA on Thursday accused the New Delhi-based Ranbaxy of falsifying data and test results of medicines produced from the Paonta Sahib facility to obtain marketing approval in the world's biggest drug market. The drug regulator had stopped granting approval for the sale of medicines produced in the facility since September 2008 pending investigation.

A Daiichi Sankyo statement said the company takes the issue very seriously. 'Both Daiichi and Ranbaxy have already formed a team to solve the issue,' it said. Referring to the Abbreviated New Drug Applications applied from the factory or all of applications based on the data of the factory, the Japanese company said that FDA letter gives the opportunity to Ranbaxy to cooperate with the agency to address the issues or withdraw the application.

'After carefully analysing the letter and information, Ranbaxy will be responding to the FDA and will continue to cooperate with the agency,' Daiichi added. Ranbaxy shares fell more than 18 per cent to Rs 169.85 on Thursday on the Bombay Stock Exchange, while Daiichi stock dropped about 10 per cent to yen 1,680 on the Tokyo Stock Exchange.