The health ministry will censure a Japanese unit of Swiss pharmaceutical giant Novartis AG for failing to report serious side effects from some of its drugs within a certain period of time, sources close to the matter said Wednesday.

The Ministry of Health, Labor and Welfare will serve Tokyo-based Novartis Pharma K.K. with a business improvement order, possibly as early as this month.

The case centers on side effects observed in around 5,500 patients, which should have been reported to the state within a few weeks of discovery.

It is the third administrative penalty to be imposed on the company over its reporting delays.

The ministry said the drugmaker has told it that the delay was due to an in-house system failure that occurred at the beginning of this year. Contacted by reporters, the company declined comment.

Novartis Pharma was handed a 15-day business suspension order in February this year and a business improvement order in July 2014 for failing to report health problems caused by its leukemia drugs by the deadline.

In July 2014, Novartis Pharma and a former employee were indicted on charges of causing a medical research team to release manipulated data in favor of the company's blood pressure-lowering drug Diovan in 2011.

Pharmaceutical firms are required by law to report to the state significant side effects of their drugs within 30 days of discovery.