EU officials have said tests carried out to establish if a birdflu virus in Romania was the strain harmful to humans have proved negative. But scientists are warning more tests have to be carried out and that it is too early to say if Romania is clear of the H5N1 virus.Romania is one of a number of eastern European countries to have been hit by an outbreak of birdflu. It has triggered fears that the form of the disease which has killed dozens of people in Asia could have arrived in Europe. Romanian authorities have said they have found no new cases but would continue culling poultry in the Danube delta to prevent the disease from spreading. Turkey has warned that it faces a high risk of further outbreaks of avian flu as it lies in the path of species of migrating birds. Meanwhile a top UN officials has cautioned that drug companies may not be able to produce enough vaccine in time to combat a possible pandemic among humans.