Health officials say they have pinpointed the source of the recent measles outbreak in Western Pennsylvania -- a traveler from India who entered the country in early March.

The number of confirmed measles cases in the region stands at six, with additional probable cases awaiting confirmation, according to the state and county departments of health and UPMC Children's Hospital.

State and county investigators and staff from numerous health care facilities have contacted thousands of people who might have been exposed to measles to assess each person's risk, officials of the three agencies announced this afternoon.

While most of those exposed have been found to be immune to the disease, some non-immune people have been asked to stay home until they are cleared of risk.

Initial exposures occurred at Children's Hospital. In addition, exposures may have occurred at the following locations and times:

Children's Hospital Emergency Department and waiting area, between 6 p.m. March 27 and 3 a.m. March 28, and between 2:30 p.m. and 5 p.m. March 28.

Alle-Kiski Hospital, Emergency Department, main lobby and ground floor public areas, between 10 a.m. and 3:30 p.m. March 28.

EMS-I Conference at Seven Springs Mountain Resort, in the Snowflake Room and the main dining room area, between 9:30 a.m. and 3:30 p.m. March 26.

Allegheny County Port Authority bus routes: 28X (Airport Flyer) -- March 24, between 10 a.m. and noon; March 28, between 2:30 p.m. and 4:30 p.m.

33X (West Busway All Stops) -- March 27, between 10 a.m. and 1 p.m.

71A -- March 24, between 11 a.m. and 1 p.m.; March 27, between 11 a.m. and 2 p.m.

Health officials believe there is no current risk of exposure at any of these places.