TEWKSBURY — A longtime town employee and her son, a newly appointed Tewksbury police officer and former School Committee member, have both resigned after irregularities were uncovered in the town’s health-insurance program.

Melanie Sitar, a decade-long worker in the Administrative Services Department, left two weeks ago, after reimbursing the town $1,850. Michael Sitar III this week tendered his resignation from the Tewksbury police force, which he had joined last year.

The town is now poised to conduct an audit “on dependents who were added to the town’s health-insurance policy or switched to COBRA coverage” between January 2007 and the middle of last month, according to a statement released to The Sun yesterday.

The case was also to be referred yesterday to the office of Middlesex District Attorney Gerard Leone, who would have the power to levy criminal charges.

The statement, which was released by Town Manager David Cressman, said that the town was first informed by Blue Cross/Blue Shield of “possible irregularities to its health-insurance program enrollment” on July 15.

Cressman declined yesterday to give more details about the alleged irregularities.

Melanie Sitar, 50, handed in her resignation and the reimbursement on July 16.

After further investigation by Cressman and Police Chief Alfred Donovan, the town launched discharge proceedings against her this week. She was officially terminated yesterday.

The Chandler Street resident was one of two employees in the Administrative Services Department. She handled employee benefits, occupational-injury compensation, medical-costs analysis, COBRA coverage, family medical leave and Medicare Part D, according to the town report.

COBRA is a federal law that allows workers who lose their jobs to temporarily keep their health-insurance coverage, though usually at a higher cost.

Sitar had run unsuccessfully for the Tewksbury School Committee in 2004, when she was defeated by Keith Rauseo.

Her son joined the committee in 2006 after an uncontested race. The 24-year-old did not run for re-election this year, saying that his new job as a Tewksbury police officer was infringing on his committee work. He also cited his upcoming wedding, which would have interfered with meetings at the height of the budget season.

Sitar and his fiancee were thinking about temporarily moving out of town, he had said at the time, because they had found it challenging to find a home they could afford in Tewksbury

He turned in his resignation from the police force on Wednesday.

The mother and son are not the only members of the Sitar family who work for Tewksbury’s town government.

Michael Sitar Jr., Melanie’s husband and Michael’s father, is a captain in the Fire Department and serves as Tewksbury’s emergency management director.

His brother, Daniel Sitar, is also a Tewksbury firefighter.