Lanxess AG shares rose the most in more than a year Monday after Warren Buffett's General Reinsurance AG group said it had acquired a stake in the German chemicals company.

The 3% holding, which was disclosed in a filing to the German stock exchange, makes General Re one of the company's five-biggest shareholders, according to FactSet data, along with Allianz Global Investors, Templeton Investment Counsel and Norway's sovereign wealth fund.

Lanxess shares surged more than 8.6% in Frankfurt trading Monday, the biggest single-day jump since October 2015, to close at €68.45 each and value the company at €6.3 billion ($7 billion).

Lanxess posted a 25% increase in both sales and operating profit in the first quarter of this year, according to the company's most recent filings, and closed a $2.7 billion takeover of Philadelphia-based Chemtura Inc. last month. 

The global chemicals sector has been awash with deals, mergers and pursuits following last year's $130 billion merger between Dow Chemical(DOW) - Get Report and DuPont(DD) - Get Report  , whcih was signed-off by the European Commission in March under the provision that DuPont sell its pesticides business in order to ensure competition in the agrochemicals sector.

"Pesticides are products that matter - to farmers, consumers and the environment," said Commissioner Margrethe Vestager in a statement. "We need effective competition in this sector so companies are pushed to develop products that are ever safer for people and better for the environment." 

DuPont said it would sell its Cereal Broadleaf Herbicides and Chewing Insecticides portfolios as well as divest its crop protection research and development pipeline and assets.

Pittsburgh-based chemicals and coatings supplier PPG Industries Inc.(PPG) - Get Report sold its remaining fiberglass operations to Japan's Nippon Electric Glass Co. Ltd. for $545 million as it remains in hot pursuit of a $30 billion mega-merger with Dutch chemicals and paint company Akzo Nobel NV (AKZOY) .