NAIROBI — The World Health Organization accused Tanzanian authorities of withholding information about suspected Ebola cases in the country this month, potentially hampering the containment of the deadly virus.

The U.N. agency’s statement Saturday was its most pointed rebuke toward any government yet during the outbreak that has ravaged nearby eastern Congo for more than a year, killing more than 2,000 people.

The WHO was made aware of the suspected cases in Tanzania shortly after one appeared this month in Dar es Salaam, the East African country’s largest city and former capital. After that, the international organization was shut out of blood sample testing and told by the government that Ebola had been ruled out, it said.

Tanzanian authorities have not offered alternative diagnoses.

“The limited available official information from Tanzanian authorities represents a challenge,” the WHO said. “Clinical data, results of the investigations, possible contacts and potential laboratory tests performed have not been communicated to WHO.”

The WHO’s statement refers to a 34-year-old doctor studying in central Uganda who returned to her native Tanzania with Ebola-like symptoms and died Sept. 8 in Dar es Salaam. Her illness was apparently contagious, as numerous contacts also became ill.

The WHO said it received “unofficial reports” that the woman tested positive for Ebola, but one of her contacts in a different city did not. The agency said it received no information on another possible case, also in Dar es Salaam. 

The Ebola outbreak that began in August 2018 is the world’s second worst, but it has remained largely confined to two provinces in eastern Congo. There have regularly been days in the past few months in which dozens of new cases have been reported.

A small number of Congolese who sought treatment in neighboring Uganda were confirmed to have the virus in that country. But the outbreak has otherwise not left Congo’s borders.

Nevertheless, Ebola is a virus that can travel far before its symptoms — which include extreme fever, vomiting blood and bloody diarrhea — become apparent. The WHO has pursued potential cases in the outbreak that has traveled as far as Dubai and China. Contacts of any suspected cases must be quarantined to prevent the virus’s spread.

Tanzania has never reported a case of Ebola. Tourism makes up a significant portion of the country’s economy, and Ebola’s presence there could lead to widespread trip cancellations.

U.S. Health and Human Services Secretary Alex Azar visited Congo last week to survey the Ebola response. Before the WHO released its statement, Azar urged Tanzania to meet its international obligations for transparency. 

“We call upon the government of Tanzania to comply with its obligation under the International Health Regulations immediately with transparent disclosure of information and full cooperation with the international health community to allow for independent verification as to the circumstances of that individual’s death,” Azar told reporters during a briefing. 

Correction: An earlier version of this article misstated Tanzania’s capital. It is Dodoma, not Dar es Salaam, which was the former capital.