A foul-smelling acid that shut down three Houston abortion clinics has the FBI investigating potential links to similar vandalism at clinics across the South.

In late May, the acid was poured into 10 abortion clinics in Florida. Five facilities were hit in Louisiana last weekend before the acid was poured in four Houston clinics on Wednesday.While the attacks are virtually identical, FBI officials said it was too soon to speculate on whether they are the work of the same person or group.

"It's really too early to tell," said Suzy Bailliere, chief of the FBI's hate crimes unit in Washington. However, "it is certainly an interesting situation seeing so many of these in such a short period of time."

All of the attacks involved butyric acid, a chemical used in perfume and disinfectant. While not life-threatening, the acid's fumes smell similar to rotten eggs and can cause dizziness and nausea.