The helicopter was taking five senior Guyanese officers to inspect troops guarding the border area that both countries claim as their own, according to Brigadier General Omar Khan, chief of the Guyanese army.
He said two crew members were also on the aircraft, a brand new Bell 412 EPI, which vanished about 48 kilometers (30 miles) east of the Venezuelan border.
Khan told reporters there were no indications that Venezuela was involved in the incident, despite the recent build-up of Venezuelan troops with heavy equipment and machinery at the border.
"We do not have any information suggesting that there was any flight by Venezuelan aircraft in that area," he said. "Speculation is not what I want to go into. Our priority is to save the lives of our officers and ranks."
Khan said that the US would help in the search for the aircraft on Thursday.