All five people killed in the attempted robbery of a vehicle used to transport money for a social welfare program in the Mexican Gulf coast state of Veracruz were police officers, officials said.

Initial reports said four police officers and a civil servant had been fatally shot in a remote rural area by assailants.

The five police officers were killed, but the gunmen came away empty-handed because the vehicle was on a return trip after the funds had been delivered.

The incident occurred Monday in Tlachichilco, a city about 400 kilometers (249 miles) from Mexico City.

The robbers used a tree to block a dirt road between the communities of Onatal Azteca and Otatitlan, and then they opened fire on the state vehicle.

The money, however, had already been distributed to recipients in Otatitlan, Veracruz police said.

The program is aimed at fighting poverty in marginalized areas of Mexico. EFE