VALLE DE BRAVO, Mexico (AP) — Five police officers were fatally shot after they stopped a vehicle in a town outside Mexico City, authorities said Tuesday.

Mexico State prosecutor Alfredo Castillo Cervantes said the municipal officers from the town of Ixtapaluca had stopped the vehicle when a taxi and a van pulled up and a group of attackers opened fire with high-powered weapons.

A member of La Familia Michoacana drug cartel who police say was responsible for collecting extortion money from bars in the area was killed in the Monday attack. Another man was shot in the head and is at a hospital under police guard, Castillo said.

Investigators think the men may be the suspects originally stopped by the officers.

Police are still trying to determine why the officers stopped the vehicle and whether they were in a negotiation with the men in the car when they were attacked. Witnesses told investigators the officers talked for several minutes with the pair before the assailants arrived, Castillo said.

La Familia, based in Michoacan state, has been spreading to Mexico state and neighboring areas as they wage a turf battle with former allies.