12:50 P.M. -- About 455 UC Davis students, nearly all freshmen, were returning to their residence halls around noon today after being safely evacuated Wednesday night when police found explosive materials in a student's room.

Only one building in the housing complex remains closed as police continue their investigation.

All campus activities are continuing as scheduled today.

Students living in the Tercero Residence Halls were evacuated immediately after the materials were found, as a precaution. They spent the night in a safe location -- the Tercero Dining Commons. (The dining commons has lounge space in addition to dining areas, and meal service was not interrupted.)

"We evacuated students as a precaution. We do not expect further disruption to the university," said Fred Wood, vice chancellor for student affairs. "We are confident that university police and other local law enforcement agencies have the situation contained."

Police arrested economics major Mark Christopher Woods, an 18-year-old freshman from Torrance, Calif., and charged him with two felonies: possession of chemicals to make explosives and possession of explosive materials on school grounds.

At the time of the evacuation, campus emergency officials conferred and determined there was no threat to wider campus safety and therefore it was not necessary to activate the emergency notification system.

Shortly after 8 a.m. today, officials did send a campuswide e-mail to direct the community to information on the UC Davis Web site and saying that campus activities would continue as scheduled.

The incident began at about 9 p.m. on Wednesday (March 5), when UC Davis police received a call from a woman who said there might be explosive devices inside a residence hall.

Police went to the room, located on the third floor of one of the Tercero halls, a cluster of buildings located on the west side of the main campus, near the junction of Interstate 80 and Highway 113.

After finding suspicious materials, police evacuated the building and withdrew to a safe distance until the arrival of other law enforcement and fire agencies, including regional bomb squads and agents of the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) and FBI.

After a search warrant was issued this morning, the bomb experts assessed the materials in the room. They removed the materials and transported them to the FBI crime lab in Sacramento for analysis.

Woods has been transferred from UC Davis Police custody to the Yolo County Jail in Woodland.

Police investigators say there is nothing to indicate that this case was related to a terrorist act. The investigation is continuing.