ENFIELD, N.C. — 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.

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.