The Government team investigating the horsemeat scandal yesterday moved into a second building associated with B&F Meats, the latest firm implicated in the Europe-wide fiasco.
Documents and computer records associated with B&F Meats were seized from offices in Thomastown, Co Kilkenny, after the B&F plant in Carrick-on-Suir was found to have shipped horsemeat to a company in the Czech Republic labelled, in the Czech language, as beef.
It comes as Agriculture Minister Simon Coveney faced opposition calls to stand aside.
Fianna Fail Agriculture spokesman Eamon O Cuiv called on the Taoiseach to set up an independent investigation.
"Today's revelations demonstrate Simon Coveney's inability to come to grips with the situation," Mr O Cuiv said.
"Since this disaster began to unfold, the minister has consistently sought to minimise the significance of the problem, rushed to declare it solved and evaded straightforward questions about when he first became aware of allegations about irregularities.
"Hoping that the problem would just go away was never going to work."
Fianna Fail leader Micheal Martin also called on Mr Coveney to step aside. In response, Mr Coveney said: "This issue needs strong political leadership as well as a detailed investigation and a strong policy response at both a national and European level. Ireland is leading that response and will continue to do so."
The latest blow to Ireland's reputation has gone around the world with the Washington Post, Fox News and other media outlets in the US carrying the story.
There has been no explanation from B&F Meats and calls to the company directors went unanswered yesterday.
It's the first time that a single company has been found to have been mis- labelling horsemeat as beef. In other cases around Europe meat suppliers have claimed they were conned by others in the supply chain.
Though B&F is a small producer, the reputational damage to Ireland is significant.
All operations at B&F Meats in Carrick-on-Suir have been suspended.
Officers of the Department of Agriculture's special investigation unit entered the plant in Carrick-on-Suir on Friday. They are liaising with the Garda National Bureau of Criminal Investigation, which has also been called in by Mr Coveney. Europol is also being briefed on the latest developments, according to a government source.
Yesterday, department investigators moved into other buildings associated with the firm near Thomastown, Co Kilkenny.
The department said the horsemeat from B&F Meats was being dispatched to a single customer "via a UK-based trader using a label in the Czech language which, when translated, refers to beef".
"I am seriously concerned about this development and the gardai have been fully appraised of this development and are working closely with my department," said Mr Coveney.
"The issue here is one of mislabelling and that will be the focus of the investigation."
The Czech authorities have been briefed and are attempting to establish where the mislabelled horsemeat ended up.
Company records dating back to 2011 show that the directors of B&F Meats are Edward (Ted) Farrell, John Barron and Michael Farrell. The company is headed by Ted Farrell.
B&F Meats is one of three companies in Ireland licensed to slaughter horses, although the plant being investigated processes and debones horse carcasses rather than slaughtering them.
In 2010 Ted Farrell came before an Oireachtas committee calling for a relaxation of the rules governing the slaughtering of horses for human consumption.
B&F Meats had a processing plant in Thomastown but it was destroyed by fire. However, there were still some offices associated with the company at the Thomastown site and that became the focus of investigations yesterday.