Attendants Nguyen Thanh Thuy, Vo Tu Quynh, Tran Thi Thu Ngan and Dang Phuong Van left detention after two other suspects were arrested for involvement in the case, according to the source.
Investigators reported that initial inquiries have so far determined that the attendants did not know that 157 out of the 327 toothpaste tubes they carried contained drugs.
"There is not enough evidence for a criminal charge," authorities announced.
Ho Chi Minh City police are looking to potentially charge a suspect or suspects with drug trafficking.
On Mar. 16, a security inspection at Tan Son Nhat Airport in Ho Chi Minh City found hundreds of toothpaste tubes containing 11.4 kg of drugs hidden within the carry-on luggage of the four women in question.
The attendants were promptly arrested after their shift aboard flight VN10 from France to Vietnam.
The suspects told the police they had agreed to transport the 60 kilograms of toothpaste tubes on the request of a person in France made via another Vietnam Airlines employee.
The four attendants said they were paid VND10 million (US$422) to bring the tubes into Vietnam.
All four denied knowing what was inside the containers.