A listeria outbreak in Europe linked to frozen vegetables produced by Belgium-based multinational Greenyard (Euronext Brussels: GREEN)  has led to nine deaths, but the company said more time is needed to establish a connection. 

The European Food Safety Authority (EFSA) said on Friday that frozen corn and possibly other frozen vegetables are the likely source of the outbreak that has been affecting Austria, Denmark, Finland, Sweden, and the U.K. since 2015.

It said that as of 15 June 2018, 47 cases including nine deaths had been reported.

The same strains of L. monocytogenes have been detected in frozen vegetables produced at a Greenyard plant in Hungary in 2016, 2017 and 2018, it said.

But Greenyard said: "Further investigation on the causal medical link between the above cases and the contamination in the production facility is required."

On June 29 the Hungarian Food Safety Authority issued a resolution to Greenyard Frozen Hungary Kft to stop all marketing and to recall from its customers and consumers all frozen products that had been produced in the plant between August 2016 and June 2018.

"Immediately following this resolution, Greenyard has taken all possible additional measures to preserve food safety, among others recall of the products, closure of the Hungarian plant and additional tests and analyses," Greenyard said.

"The recall is a precautionary measure and does not imply that recalled products are contaminated."

The company's share price fell by as much as 30 percent when the stock market opened on Monday, The Brussels Times reported.

Trade in the Greenyard share resumed on Monday morning, opening at 8 euro, it said. In the afternoon the stock even dropped to 7.5 euro: a loss of 35 percent. The publication reported the share is at its lowest level since the summer of 2012.