An undisclosed number of Aetna Inc. employees, including case managers, received layoff notices Wednesday at the health insurer's Blue Bell office. One employee said that seven out of 18 supervisors lost their jobs, and each supervisor oversaw a staff of 15 to 20.

Aetna spokeswoman Cynthia Michener declined to say how many people were laid off in Blue Bell. The layoffs, she said, were related to Aetna's $8.7 billion acquisition of rival insurer, Coventry Health Care Inc., completed in May 2013.

Aetna, based in Hartford, Conn., employed 35,000 in December, 2012, adding 14,400 Coventry employees. Aetna has said it planned to lay off 3,000 workers by 2015 as operations were integrated.

By Dec. 31, the combined companies employed 48,600. Blue Bell workers were given the option of leaving immediately or staying until Friday. Other categories of workers may be able to stay on through March. - Jane M. Von Bergen