Meredith Davis, a spokeswoman for the Bureau of Alcohol, Tobacco, Firearms and Explosives, said officials had "successfully traced" the four guns recovered in connection with the San Bernardino shooting and determined that two of the weapons were purchased legally.
The guns were bought by an individual associated with the investigation, Davis said but declined to name the person.
"Agents continue to investigate leads concerning the two additional firearms," Davis said.
Police officials said that two suspects, Syed Farook and Tashfeen Malik, were armed with two assault rifles and two semiautomatic handguns.
The assault rifles were a .223-caliber DPMS Model A15 and a Smith and Wesson M&P15. The handguns were manufactured by Llama and Smith and Wesson, respectively.