Medical officials in Congo suspect that an Ebola outbreak has spread from the spot where the disease was first identified to a neighboring province, officials said Friday.

Samples from two cases suspected as Ebola from Congo's Kasai Oriental province have been sent to a lab in the United States for testing, said Dr. Benoit Kebela, secretary general of Congo's health ministry.

Ebola has so far been confirmed only in neighboring Kasai Occidental province, where at least five samples have tested positive. About 40 samples are still pending.

At least 167 people have died — though it is not clear how many of Ebola — in the affected region of Kasai Occidental over the last four months, and nearly 400 have fallen ill, according to Congolese health officials.

Diagnosis is difficult. Experts say many of the cases reported could be shigella, a diarrhea-like disease, or typhoid. At the early stages, both diseases have symptoms similar to Ebola.

It is the first major outbreak of the deadly disease in years. Teams have arrived from the U.S. Centers for Disease Control to help and the World Health Organization has put out a call for doctors.

"There are lots of suspected cases because of the fear that has taken over Kasai Occidental and almost the whole country, but all fevers with blood are not Ebola," Kebela noted.

Kebela said the latest samples came from the area around the village of Mwene Ditu, about 100 kilometers south of the provincial capital of Mbuji-Mayi and more than 300 kilometers from the village of Kampungu — the site of the confirmed cases. A train line that runs between the two provinces passes through Mwene Ditu, but Kebela said he did not know of any contact between the infected people in Mwene Ditu and people in Kampungu.

The government has quarantined the area around Kampungu.

Ebola quickly kills up to 90 percent of those infected through massive blood loss, and has no cure or treatment. It is spread through direct contact with the blood or secretions of an infected person, or objects that have been contaminated with infected secretions.

Congo's last major Ebola outbreak struck in Kikwit in 1995, killing 245 people. Kikwit is about 185 miles (about 300 kilometers) from the site of the current outbreak.

WHO says more than 1,000 people have died of Ebola since the virus was first identified in 1976 in Sudan and Congo. Primates, hunted by many central Africans for food, can carry the virus.