* Polish ingredient in burgers contains 75 pct horse DNA
* "Another depressing saga" for Ireland, says minister
DUBLIN, Feb 4 (Reuters) - Burgers containing horse DNA have been discovered at a second major plant in Ireland, the country's agriculture department said on Monday, again pointing the finger at Poland as the country of origin for the raw materials.
Food companies such as Tesco and Burger King last month found that beef products supplied by an Irish firm contained horse DNA, a scandal that has hit retailers with a wave of bad publicity and left Ireland's 2 billion euro ($2.7 billion) beef industry reeling.
Results of tests on a Polish meat ingredient at Ireland's Rangeland Foods, a supplier of frozen burgers to restaurants, caterers and pubs including local fast food chain Supermac's, contained 75 percent horse DNA, the agriculture department said in a statement.
"This isn't a huge surprise, it's another depressing saga that has put Irish food in the headlines for all the wrong reasons," Irish Agriculture Minister Simon Coveney told national broadcaster RTE.
"It's not a surprise to me because this is the same product that has been going into Silvercrest," he said, referring to the plant run by Ireland's most powerful beef baron Larry Goodman, the first whose burgers were found to contain horsemeat.
Coveney's department said Rangeland has suspended production pending the outcome of an investigation and the company has indicated that none of the products, which were imported through a meat trader based in Ireland, had entered the food chain.
Rangeland, based in the northern county of Monaghan, exports burgers to Britain, Sweden, Spain, Belgium, the Netherlands, Greece and Cyprus. Coveney said the product containing the horse DNA was destined for the catering industry outside Ireland.
Initial tests on burgers produced by another Irish company, Liffey Meats, also tested positive for low traces of horse DNA, although further tests came back clear.
The minister said the only two other burger manufacturers in the country had both confirmed they have not used any Polish products, and that their products are 100 percent Irish sourced.
He has also asked the police and the fraud squad to join in the investigation and said the government would take legal action against those responsible if necessary.
Silvercrest - a subsidiary of Europe's largest beef exporter ABP Foods which is based just 6 kilometres (3.7 miles) from Rangeland - has lost its contract to supply both Tesco and Burger King with burgers.
Burger King, one of the most popular fast food chains in Britain and Ireland, said last week its affected burgers never reached any eateries. Tesco withdrew a number of products from its shelves, including one sample where horse meat accounted for about 29 percent of content.
Smaller retail chains Aldi, Lidl and Iceland have also sold beef products found to contain horse DNA.
Poland's veterinary authority found no signs of horse meat in samples from five slaughterhouses that were sending beef to Ireland and is awaiting results from the sixth, state news agency PAP reported on Friday.
Food safety experts say horse DNA poses no added health risks to consumers, but the discovery has raised concerns about the food supply chain and the ability to trace meat ingredients.