LONDON: Brazilian officials say they’re sending a set of samples related to the Zika outbreak to the United States, a move which follows complaints that the country was hoarding disease data and biological material.

Thursday’s announcement came only hours after The Associated Press revealed that international health officials were frustrated at Brazil’s refusal to share enough viral samples and other information to answer the most worrying question about the outbreak: Whether the disease is truly causing a spike in babies born with abnormally small heads.

US and UN officials told AP that Brazil probably shared fewer than 20 samples when experts say hundreds or thousands of samples are needed to track the virus’ evolution and develop accurate diagnostics, drugs and vaccines. Many countries’ national laboratories are relying on older strains from outbreaks in the Pacific and Africa, the AP found.

After the story’s publication, the World Health Organization sent out a flurry of messages acknowledging that existing data-sharing mechanisms were deficient.