MEXICO CITY >> A Mexican army general said his forces are increasingly coming under fire from drug traffickers protecting opium poppy plantations in Oaxaca state, where opium growers are moving production to take advantage of mountainous terrain and impoverished villages.

Gen. Alfonso Duarte Mugica said Wednesday that army patrols were fired at twice this week as they tried to cut down poppy plantations in western Oaxaca.

On Monday, an army helicopter searching for poppy fields was hit by gunfire from the ground, damaging the fuel tank. The chopper landed safely.

He said a third army patrol was blocked from reaching about 30 poppy fields they could plainly see in the distance, by a demonstration of Indian residents, mostly women and children. Armed with only sticks and machetes, the Triquis stood in front of soldiers and refused to move.

Duarte Mugica said the farm communities were being recruited by the cartels and acknowledged the army is walking a thin line in Oaxaca, where Indian communities jealously guard their territories and their rights.

Any confrontation with Indians would be a public relations disaster.

“The presence of the military in this and other areas of the state is because of the important presence of opium poppy and marijuana fields that the drug cartels have been planting in the mountains of Oaxaca,” Duarte Mugica said. “I want to repeat that the Defense Department and particularly the soldiers of the 8th Region are respectful and sympathize with the traditions and practices of each of the Indian groups in Oaxaca state.”

The shift to Oaxaca has officials worried. The state is better known for its colonial capital and beaches, but its large impoverished Indian population and mountainous terrain could make it ideal for growing opium.

The Mexican army faces a delicate task in moving into Oaxaca’s notoriously conflictive Triqui Indian communities.

The region has seen three Triqui groups locked in a decades-long armed struggle that has led to dozens of killings.

One of those groups, known as the Triqui Unification and Struggle Movement, demanded this week that the army be withdrawn completely from the area.

“Now we have the Mexican army coming in by land under the pretext of searching for poppy plantations. They staged incursions all last week in our territory, and found only corn fields and more cornfields,” the movement said in a statement. “Get the army out of Triqui territory! No to the militarization of our country’s indigenous lands!”

The idea that authorities are finding only corn fields is questionable; in recent months, unusually large poppy fields have been found in Oaxaca, whereas opium production used to be centered in neighboring Guerrero state.

Increasing army raids in Guerrero — and the presence of a large number of violent small drug gangs who fight among themselves for the business of buying opium paste from farmers — have apparently made Oaxaca more attractive. And Oaxaca Indian groups like the Triquis have a long history of armed resistance. Dozens have been killed in the violence, including a Finnish rights observer.

One striking aspect is the size of the opium fields the army is finding in Oaxaca. In Guerrero, such plantations rarely measure more than an acre (half hectare).

But in February, federal police found a pair of poppy fields in other part of Oaxaca that measured almost 37 acres (15 hectares).

Altogether, in the last year, Duarte Mugica said troops had destroyed a total of 1,747 acres (707 hectares) of poppy and marijuana fields, most of them poppies.