Samsung shares fell after antitrust regulators in South Korea told the biggest conglomerate in the country to lower is cross-shareholdings that had expanded due to a controversial merger between two units earlier this year.

Samsung C&T dropped by 4.8% while Samsung SDI was down by 3.1% after a Sunday announcement by the Fair Trade Commissions said Samsung SDI must trim its share in Samsung C&T or it needed to take measures that would weaken the cross shareholdings that were built up through a deal in September.

The group must comply by March or will face a stiff penalty. Samsung SDI, the unit that makes batteries, has said it would be selling a stake of 2.6% in Samsung C&T, the defacto holding part of the group, in order to comply.

Samsung officials said they were considering possibly asking the FTC to give them an extension on the March deadline.

In September, Samsung C&T merged with Cheil Industries in a deal that helped the founding family’s control remain in Samsung, overcoming heavy opposition from Elliot Associates an activist hedge fund from the U.S.

Prior to the merger, Samsung SDI had a stake of 3.7% in Cheil and a stake of 7.2% in Samsung C&T and following the deal of all stock, it has a stake of 4.7% in the combined company, which has taken the Samsung C&T name.

Public pressure is increasing on chaebol or family operated conglomerates in South Korean to simply the complex ownership structures they hold and the poor corporate governance has been said to be a factor in constraining the valuations of the companies in the country.

Analysts have said that the push by the FTC could weaken the control of the Lee family slightly in Samsung C&T, but they said it should not endanger the hold the family has on units like Samsung Life Insurance or Samsung Electronics.

The Lee family, as well as a group of affiliates, together have a stake of 39% in Samsung C&T, which has a stake of 3.5% in the biggest jewel of the group – Samsung Electronics.