San Diego police say this video shows two young women suspected of setting fires in the Price Center at UC San Diego.

SAN DIEGO - A 22-year-old UC San Diego student has been arrested on suspicion of an on-campus arson. A second suspect is being sought, police said Friday.

Hoai Vi Holly Thuy Nguyen was arrested on campus Tuesday on suspicion of setting two fires Dec. 3 at the Price Center, which houses restaurants and meeting and event spaces.

Surveillance cameras show two young women entering the center at a time when it was occupied by several hundred students, police said.

The cameras show the two setting fires on the first and second floors, police said. After setting the first fire, the two fled, then returned wearing different clothing, police said.

The fires were quickly extinguished and there were no injuries.

Nguyen pleaded not guilty Thursday in San Diego County Superior Court to two counts of arson.

No motive for the arson attempts was disclosed.

[Updated 1:30 p.m. PST Feb. 7: Police said one possible motive is a kind of protest against “new development at the location.” In recent weeks, a controversy has arisen on campus over Starbucks’ planned move into an empty space at Price Center left by another coffee vendor, according to the student newspaper.

Some students have accused Starbucks of using corporate influence unfairly to be designated as complying with ”fair trade practices,” which include pay scales for employees and environmental sensitivity when buying raw materials.

The fires occured the same day that the center's advisory board, on a split vote, approved Starbucks' bid to move in.]

Anyone with information leading to the arrest of the second suspect is asked to call Crime Stoppers, (888) 580-8477. A reward of up to $10,000 is offered for information leading to an arrest for felony arson.

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tony.perry@latimes.com