Bolivian police and military forces used armored vehicles and helicopters to unblock access to a major gas plant in the city of El Alto on Tuesday, a show of strength after blockades at the facility had cut off fuel supply to nearby La Paz.

Helicopters flew above roads around the Senkata gas plant, operated by state-run YPFB, which were blocked with piles of burning tires, according to a Reuters witness. Protesters are demanding the return of unseated leftist leader Evo Morales.

Morales resigned on Nov. 10 amid anti-government demonstrations and rising pressure over vote-rigging allegations after an audit by the Organization of American States (OAS) found serious irregularities in an Oct. 20 election.