Air marshal attacked with syringe at Nigeria airport

A federal air marshal was attacked in Nigeria by someone wielding a syringe that contained an unknown substance, officials say.

The unidentified marshal may have been attacked because he was American. The FBI is investigating the incident, which took place Sunday, but it is not considered to be a terrorist attack.

The assault took place at Murtala Muhammed International Airport in Lagos. The Transportation Security Administration released a statement saying the marshal was attacked while boarding the aircraft, which was about to leave Lagos for George Bush Intercontinental Airport in Houston.

The condition of the marshal, who was on-duty at the time, is unclear. However, a law enforcement official said he was stabbed in the arm. It is not known if he was injected but the injury is being treated as if he were.

The Centers for Disease Control and Prevention set up a screening when the United Flight 143 arrived in Houston early Monday.

"The victim did not exhibit any signs of illness during the flight and was transported to a hospital upon landing for further testing," the FBI said in a statement. "None of the testing conducted has indicated a danger to other passengers."

Federal air marshals work under the Transportation Security Administration and wear plain clothes instead of uniforms.