The source, who spoke on condition of anonymity due to restrictions on talking to media, said thirteen suspects were taken into custody, whereas one another remained at large.
Earlier, Adana Chief Public Prosecutor Ali Yelden said among the suspects were the dormitory manager, three teachers, and two caretakers.
At least 12 bodies were recovered after the fire broke out in a private girls' dormitory in the Aladag district late Tuesday.
According to reports, 31 students were staying at the secondary school dormitory when the blaze erupted, Deputy Prime Minister Veysi Kaynak said Wednesday.
Some 24 people, including eight adults, were either affected by smoke or hurt while trying to escape the burning building.
The fire likely broke out due to an electrical fault, according to the latest information, Kaynak said.
He also denied claims that the fire escape was unavailable, thus preventing students from escaping the burning building.
He said the building was legal and had licenses and permits from the Education Ministry and that the latest official inspection was carried out in June.
Turkish President Recep Tayyip Erdogan, Parliament Speaker Ismail Kahraman, and Prime Minister Binali Yildirim all expressed their pain over the tragedy and offered their condolences.
Azerbaijani President Ilham Aliyev also sent a letter of condolences to Erdogan, saying:
"My dear brother, we are deeply sorry about the loss of lives in a student dorm in Aladag. We share your pain and offer condolences to the families of the victims and our brother Turkish nation."
Turkey's opposition party leaders also expressed condolences to the victims' families.
On Twitter, Republican People's Party (CHP) leader Kemal Kilicdaroglu called his pain over the incident "indescribable."
Devlet Bahceli, leader of the Nationalist Movement Party (MHP), said in a written statement that the event was "a total disaster."
Bahceli urged authorities to find out how the fire broke out and if there was any neglect involved.
Interior Minister Suleyman Soylu, Family and Social Policies Minister Fatma Betul Sayan Kaya, and Education Minister Ismet Yilmaz visited the victims' families Wednesday.
Families of most of the deceased students live in the rural areas of the district. They were staying at the dormitory as a daily commute would have been too time consuming.
The last time they visited their families was following last week’s TEOG high school entrance exam on Nov. 23-24.
Police are investigating the site of the fire, with security measures around the building.
The public prosecutor’s office in Kozan, another district in the province, said a thorough investigation is underway. Three prosecutors have been assigned to investigate the incident, the office said.
No "negative report" for dormitory
Education Minister Yilmaz on Wednesday said there had been no "negative report” about the dormitory during an inspection in June.
“A year ago, a general inspection was conducted. Also, local authorities carry out inspections twice a year,” Yilmaz told reporters in Adana Wednesday.
“We will take lessons from this horrible incident so that we will never experience this pain again,” he said.
“They [students] were our children. They were our future,” the minister added.