ENFIELD, N.C. (AP) – Officials in North Carolina say the FBI has joined the investigation into a home invasion in which four elderly people were shot and killed nearly two weeks ago.

Local media outlets report Halifax County Sheriff Wes Tripp confirmed the FBI’s involvement this week, although he offered no other details.

Tripp also said the reward for information in the case is now in excess of $50,000, though he didn’t provide an exact amount. He said a fund has been set up to defray medical costs for a dog which belonged to Janice and James Harris and was injured during the attack.RELATED: Sheriff: 2 elderly couples shot to death in Halifax County home invasion

Investigators have said the two married couples had been sitting around a kitchen table playing cards when they were killed sometime between Aug. 20 and 21.

James Harris was killed along with his wife and two others.

According to an ATF database, J and J Gunsmithing was a federally licensed firearm business as of July 2017. The gunsmithing business was registered to Harris at the same address where the killings occurred.

The other victims were identified as Janice Harris, 72, James Whitley, 76, and Peggy Whitley, 67.