Guyana’s security forces said a patrol boat escorting election officials and ballot boxes came under fire Sunday from across the Venezuelan border, a day before the country’s general election.

The incident happened around 2:30 p.m. on the Cuyuni River in the oil-rich Essequibo region, a disputed area at the center of the Guyana-Venezuela border feud.

In a joint statement, the Guyana Defence Force and Police said the patrol was moving along the Upper Cuyuni River in Region 7 when shots were fired from the Venezuelan shore near Bamboo. Security forces fired back before withdrawing the convoy.

All nine election officials on board were unharmed, and the ballot boxes were delivered to polling stations as planned.

“The Joint Services remain alert and continue to coordinate closely with the [Guyana Elections Commission] to ensure the security of all election-related operations. An investigation into the incident is underway,” the joint statement added.

Essequibo, a 61,600-square-mile (159,500-square-kilometer) region administered by Guyana for more than a century, is claimed by Venezuela, which held a 2023 referendum backing its annexation. Guyana has brought the dispute before the International Court of Justice, a process Caracas rejects.

The election pits President Irfaan Ali of the People’s Progressive Party/Civic against opposition leader Aubrey Norton and businessman Azruddin Mohamed. Ali, boosted by an oil-fueled economic boom that has multiplied Guyana’s GDP nearly fivefold since 2020, is widely seen as the frontrunner.