Raleigh, N.C. — North Carolina health investigators have found no sign of the swine flu in 20 suspected cases they've tested, but officials continued Wednesday to gather specimens as the virus spread to other states.

Dr. Jeffrey Engel, the state health director, said lab tests have found only the seasonal flu in three cases that investigators had been monitoring.

“Our state lab has received 41 samples to date (and) 20 have tested negative. (The other) 17 are still in the hopper,” Engel said.

Authorities have confirmed nearly 100 swine flu cases in 10 states, ranging from California to New York. There have been no cases in the South. Swine flu is suspected of killing more than 150 people and sickening more than 2,400 in Mexico.

"Everyday we go without a confirmed case is good news,” Engel said.

Engel said the state will soon begin receiving a portion of the national stockpile of anti-viral medications and supplies such as masks. He said those will be distributed to local sites.

Engel also said the state will soon receive the reagent material that's necessary to confirm the presence of swine flu in the state. Currently, the state can test to determine if a patient likely has swine flu, but final lab work must be sent to the Centers for Disease Control and Prevention.

Lab investigators were working in two shifts to test nasal swabs coming in from all over the state.

"We do have a very robust system for looking for seasonal influenza. So, during peak season, our lab is able to process a large number of samples," said Dr. Zach Moore, a respiratory disease epidemiologist for the North Carolina Division of Public Health.