A college student has been released and won't face charges after trying to drive onto Fort Sam Houston over the weekend without proper credentials, causing a nearly four-hour lockdown.

Officials at the military installation in San Antonio said Monday that investigators inspected the student's vehicle and determined it posed no threat.

The San Antonio-area man, who has not been identified, posed no security risk, military officials said without offering further details.

The suspect was alone in his car when military police pulled him over after a brief pursuit. He had no weapons or explosives in his vehicle, said Joint Base San Antonio spokesman Alex Delgado.

Fort Sam Houston, which sprawls across northeast San Antonio, includes the largest Department of Defense hospital in North America.

It is also the headquarters of several significant commands, including U.S. Army North, U.S. Army South, and the U.S. Army Installation Command.

The lockdown lasted for 3-1/2 hours. Delgado said everything was operating normally on the post on Monday.

The driver was stopped by post officials on Sunday afternoon. Officials said the students had tried to access the base through one of its gates. The base encompasses about 3,000 acres. The lockdown was lifted around 9 p.m. Sunday.

502nd Air Base Wing spokesman Alex Delgado said the male student is not in the service and the vehicle did not contain any explosives or weapons. There were no other passengers in the vehicle

Fort Sam Houston is a highly secure facility with guards posted at all vehicle entrances.