File photo: Leon Nicholas.

Johannesburg - Shares of South Africa's Adcock Ingram surged more than 4 percent in early trade on Friday on news top shareholder Bidvest Group is looking to raise its stake in the drugmaker.

Bidvest, a conglomerate with businesses ranging from mops to shipping, owns 34.5 percent of Adcock, South Africa's second-largest drugmaker. Bidvest intends to increase that to more than 50 percent, according to a document from South Africa's competition regulator seen by Reuters on Thursday.

“The Bidvest bid has involved two stages. The second stage is to acquire further shares beyond the 34.5 percent, which presumably, depending on the take-up of the offer, would take Bidvest's holding to above 50 percent,” the document said.

Bidvest Chief Executive Brian Joffe has been trying to take control of Adcock since March 2013, seeing a chance to turn around another underperformer and add painkillers to a wide variety of products.

Joffe went direct to Adcock shareholders in December last year with a 4 billion rand ($371 million) cash offer for the initial 34.5 percent, sinking a rival bid from Chile's CFR Pharmaceuticals.

Adcock shares were up 4.7 percent at 51.28 rand at 0725 GMT, while Bidvest shares were up 0.5 percent at 291.43 rand.