INDIANAPOLIS — An Indiana county at the heart of an H.I.V. outbreak has seen a “significant increase” in the number of cases more than two weeks into a short-term needle exchange program, state health officials said.

There are now 120 confirmed H.I.V. cases and 10 preliminary positive cases tied to Scott County, the Indiana State Department of Health said on Friday. That is up from 106 the previous week.

Health officials who declared an epidemic last month have said that they expect the number of cases to rise as more people are tested. The Centers for Disease Control and Prevention sent staff members to Indiana last month to help with testing, the Health Department said in a news release. The growing number of cases could put pressure on Gov. Mike Pence to extend the 30-day needle exchange program that he approved on March 26.

A spokeswoman for the governor, Kara Brooks, said on Friday that Mr. Pence was reviewing reports and recommendations from health officials and would decide within the next few days whether to extend the program beyond April 25.