A Pakistani police spokesman says gunmen have killed three women working on a polio vaccination campaign, along with their driver.
The women's driver was also killed in the attack on November 26 on the outskirts of Quetta, a western city near the Afghan border.
Police spokesman Shahzada Farhat said the women and their driver were waiting for a police escort to arrive when two men on a motorcycle pulled beside them and opened fire.
Militants have frequently targeted people involved in dispensing polio vaccinations, claiming the immunization program is a cover for spying.
The attacks have contributed to an increase in polio cases in Pakistan, which now stand at a 15-year high, making Pakistan one of only three countries in the world where polio remains endemic.
The World Health Organization has registered 235 polio cases in Pakistan this year.
Based on reporting by Reuters and AP