A Hercules man monitoring his house from his cell phone at work was able to describe an intruder, who authorities said is still on the run.

Around 12:30 p.m. Wednesday, officers arrived at a house in the 100 Block of Ash Court after an alarm activated at the residence, said Officer Connie Van Putten, a Hercules police spokeswoman.

The officers learned the homeowner was surveying his home from his cell phone after the alarm activated and the company contacted him, so the man was able to immediately provide a description. The resident installed the high-tech surveillance system after losing jewelry and a safe when his home was burglarized on Oct. 21, Van Putten said.

In this incident, the resident lost jewelry of an undetermined value.

The burglar was described as a man in his 20s wearing a blue shirt, dark pants and a beanie.

Officers saw the windows of a rear bedroom and a bathroom were open in the home and determined the man had fled, Van Putten said.

After establishing a perimeter around the home, officers called for a K-9 unit. The police dog, tracked the man over a back fence and onto Redwood Road but lost the trail, police said.

Officers viewing surveillance video described the man as 18 to 20 years old and 6 feet to 6 feet 3 inches tall, with a thin build and possible goatee, police said. He wore a royal blue V-neck T-shirt with a white shirt underneath, along with dark pants, white shoes and a black, white and gray beanie.

Anyone with more information on the case can call the Hercules Police Department at (510) 724-1111.

Jenna Lyons is a San Francisco Chronicle staff writer. E-mail: jlyons@sfchronicle.com Twitter: @JennaJourno