A couch fire early Monday was the fourth arson at the University of Arizona's Pueblo de la Cienega Residence Hall since mid-October, authorities said.

The UA Police Department and Tucson Fire Department are investigating, said TFD Capt. Barrett Baker.

No one was injured in the fires, which began Oct. 20, said Sgt. Juan Alvarez, a UA police spokesman. The fires have burned furniture and kitchen appliances, he said.

Pueblo de la Cienega, 621 N. Highland Ave., houses 238 students. On average, 80 percent of students in the halls are freshmen.

Tucson fire records say:

• Nov. 12 at 1:30 a.m., a smoke alarm sounded. Firefighters found a couch in a lounge on fire.

• Oct. 26 at 3:30 a.m., a water flow alarm went off. Firefighters found a sprinkler head discharging water in a smoky TV lounge. A couch fire had been put out by the sprinkler system.

• Oct. 20 at 11:11 a.m., firefighters found a microwave was smoking.

The fourth date was not released by Alvarez. He said investigators do not want to jeopardize the case by releasing information.

UA Residence Life has been communicating with residents by email since the fires started, and "working with campus health to bring counselors over to talk to the students," said Dana Robbins-Murray, a Residence Life spokeswoman. "We are taking this very seriously, and our No. 1 priority is to ensure the safety of our residents." On Tuesday, a letter was sent to students' parents discussing the situation and what is being done, she said.

The hall's front desk is now being manned 24 hours, seven days a week, and the staff increased "walk-throughs," she said. UAPD has also increased patrols.

UAPD detectives ask that anyone with information about the fires call 911, 88-CRIME or UAPD's tip line at 626-0066.

Contact reporter Carmen Duarte at 573-4104 or cduarte@azstarnet.com