11:30 A.M. -- All scheduled activities continued today at UC Davis after the events of the past two days, when 455 students were evacuated and explosives were safely removed from a campus residence hall.

Students returned to their rooms at midday on Thursday.

UC Davis freshman Mark Christopher Woods, 18, was released from the Yolo County Jail late Thursday after posting $100,000 bail. Woods, who lived in the residence hall room where the explosives were found, faces two felony charges: possession of chemicals to make explosives and possession of explosive materials on school grounds.

The joint investigation continues, led by the UC Davis Police Department and including the Sacramento regional bomb team, the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) and the FBI.

"The investigation will continue with additional analysis of the chemicals recovered in the student's residence hall room," which were taken Thursday to the ATF's Walnut Creek forensic laboratory, said Lt. Nader Oweis of the UC Davis Police Department. "What made this a safe and productive law-enforcement operation was the collaborative effort involving local, state and federal agencies."

Because Woods was arrested on felony charges that threaten campus safety, he has been referred to the campus Office of Student Judicial Affairs. Disciplinary policy dictates that a student facing such charges immediately be placed on interim suspension and not be allowed on campus until the conclusion of university, law enforcement and judicial proceedings. A student's status will be evaluated depending on the outcome of the university investigation and any prosecution.

All campus activities continued as scheduled on Thursday with no disruption to classes or campus business.

"Campus police and fire officials evacuated one portion of our student housing complex as a precaution, and we commend those students for their cooperation with authorities throughout the evening," said Fred Wood, vice chancellor for student affairs. "The evacuation went smoothly, as did their return back to their rooms. The campus is providing support to those students on a case-by-case, as-needed basis for any missed classes or exams."

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

Police went to a room on the third floor of one of the Tercero Residence Halls, a cluster of buildings each housing 65 students located on the west side of the main campus, near the junction of Interstate 80 and Highway 113.

Woods was in the room and was detained by UC Davis police shortly after they arrived. After finding suspicious materials, campus police and fire officials evacuated the Tercero complex as a precaution until the arrival of other law enforcement and fire agencies.

The officers determined that the situation was contained to the housing complex, and that there was no further threat to the safety or security of the campus community that required a campuswide activation of a new emergency notification system.

Woods had not made any threats to harm people on campus, and was cooperative with investigators in describing the materials in his residence-hall room, campus police said.

The evacuated students spent the night in the nearby Tercero Dining Commons. (The dining commons has lounge space in addition to dining areas, and meal service was not interrupted.)

Shortly after 8 a.m. Thursday, campus officials did use the notification system to send a campuswide e-mail to let students, faculty and staff members know that the campus was secure and that activities would continue as scheduled.

After waiting for a search warrant to be issued Thursday morning, the hazardous materials experts assessed the substances in the room. By noon, the Sacramento regional bomb team, together with the campus Office of Environmental Health and Safety, had catalogued and removed the materials from campus. Five plastic bins the size of milk crates, containing powders and chemicals, were taken away for further analysis and as evidence.

Tercero residents were then allowed to return to their rooms.