The gunmen seized the hostages during a bungled bank raid on Monday morning in the town of Altagracia de Orituco in central Venezuela.
The robbers are demanding an ambulance to make their escape along with a number of hostages. The demand has been rejected by the authorities.
"The robbers are refusing to negotiate and have rejected all our alternative offers," Ricardo Arciniegas, the public prosecutor heading negotiations was quoted as saying.
Neither the gunmen, nor the hostages, who have been allowed to phone their relatives, are reported to be hurt, but they are tired and lack drinking water.
Relatives and loved ones of the hostages spent the night near the bank which is surrounded by hundreds of police officers.
The incident is taking place in a branch of Banco Provincial, which is a subsidiary of Spain's Bilbao Vizcaya Argentaria.