FOXBORO - Longtime Police Chief Edward O'Leary underwent heart bypass surgery Monday and is expected to miss six to eight weeks of work.

Deputy Chief John Chandler will run the department during O'Leary's absence.

The surgery was not prompted by an emergency, and that O'Leary had prepared for it over the past three weeks, Chandler said.

"He came through with flying colors," Chandler said Monday. "Now starts the healing process."

O'Leary scheduled the surgery at a Boston hospital after a battery of tests revealed "a few blockages," Town Manager Andrew Gala said. O'Leary had not complained of pain or other symptoms, Gala said.

"He's in pretty good condition. Hopefully, he gets through this with no complications," Gala said.

O'Leary is expected to be discharged Friday or Saturday, the town manager said.

The chief's medical leave started Monday.

It was the first medical leave for O'Leary since he became chief in 1985, Chandler said.

O'Leary, a Foxboro native, joined the police force during the mid-1970s as a patrolman.

Chandler became deputy chief last spring, when the post was added to the police budget.

Chandler had been O'Leary's second-in-command for several years. Chandler also oversaw the department when O'Leary was out of town or on vacation.

Chandler said he has offered the department's support to O'Leary's wife, Claudia.

"We're here to help in any capacity," Chandler said.