Authorities are ill-equipped to tackle drug smuggling in Guinea-Bissau
Guinea-Bissau's justice minister has said she has received death threats over the arrest of five people suspected of drugs trafficking.
Carmelita Pires said she was scared but the government would not be intimidated and would continue investigations.
Her comments came two days after Guinea-Bissau's attorney general also said he had received death threats.
The arrests were made after at least one plane thought to have arrived from South America was seized last month.
Authorities arrested three Venezuelans as well as the head of air traffic control at the airport and his deputy.
Antonio Mazzitelli, West Africa director of the UN Office of Drugs and Crime, said no drugs had been found on the plane - despite reports that hundreds of kilos of cocaine had been seized.
Drug-sniffing dogs had indicated the plane was carrying cocaine, but authorities had to wait five days before seizing it, he said.
The incident reportedly involved a stand-off between judicial police and the army, who tried to stop the police boarding the planes.
Ms Pires said she had received two anonymous telephone calls warning her that she was "talking too much" and that she was "digging her own grave".
"I will not turn my back on this fight. I will not relinquish my responsibility," Ms Pires said.
"But I'm scared. Who wouldn't be?"
Attorney General Luis Manuel Cabral said earlier this week that senior politicians and military figures did not want the investigation to proceed.
The UN has warned that West Africa has become a hub for the transport of cocaine from South America to Europe, with at least 50 tonnes of cocaine shipped through the region every year.
It has also said drug traffickers are corroding the fragile states of West Africa by corrupting politicians and law-enforcement agencies.
Mr Mazzitelli said anti-drugs operations were beginning to work but needed more support, including physical protection for those involved.