A federal air marshal was taken to a hospital in Houston for tests after he was stabbed with a needle while at an airport in Nigeria, according to Click2Houston.

A group of federal agents in street clothes were about to walk through security at the Lagos airport on Sunday when they were approached by a group of men. Sources said one of them stabbed a needle into an agent's arm and then they took off running.

The agent allegedly pulled the needle out of his body and stored it in a container for safekeeping. He boarded the flight that he was scheduled to and landed at Houston's Bush Intercontinental Airport. He went to a hospital and physicians tested him for several transferable diseases, including Ebola and HIV.

The marshal, who has not been identified, did not exhibit any signs of illness during the flight and the subsequent tests did not indicate the marshal was a danger to other passengers, officials said, according to NBC News.

It appeared the attacker did not know the victim was an air marshal and it may have been a robbery attempt, sources told NBC News. According to the FBI, the Centers for Disease Control and Prevention conducted an on-scene screening of the victim when United Flight 143 landed in Houston early Monday morning."

Homeland security expert Joan Neuhaus Schaan said the reason for the attack lies with whatever was in the syringe, according to Click2Houston.

"Was it something intended to just harm that person, who they certainly thought was American, who they may or may not have known he was a U.S. marshal, or was it something that is contagious that they then hope to spread to the United States," she said, according to Click2Houston.

The FBI is now investigating the incident and it plans to test the needle. It could take two days for the test results to come back from the lab.

The federal marshal has been discharged from the hospital and is at home recovering.