Environment secretary Owen Paterson said his Romanian counterpart was convinced meat had been packed and correctly labelled when it left the country.
But Mr Paterson added: "The fact is, we do not know yet, and we need to get absolutely clear where the problem has occurred and get it sorted."
When he was asked why UK local authorities could not get tests on meat going to schools and hospitals tested before April, he said: "There is a limit across Europe and across the world in laboratory capacity. We would all like these tests to be done as fast as possible."
A leading food scientist says the rule change that sparked the horsemeat beef scandal affected lamb products too, and they should be tested.
Retailers and the Food Standards Agency held an emergency meeting today to decide how to proceed with the horsemeat scandal.
The government has called an emergency meeting with retailers and the Food Standards Agency to discuss the horsemeat scandal.