Khalid Abu Bakar said that each grave, near the town of Wang Kelian, may contain the remains of more than one person, according to Bernama
, the Malaysian state news agency.
"(Authorities) found 139 suspected graves. They are not sure how many bodies are inside each grave," he told reporters at a news conference.
The bodies are expected to be exhumed Monday.
Khalid said police found 28 illegal camps, the largest of which may have held as many as 300 migrants. The fact that the camp was fenced and guarded by sentries shows that the trafficked people were captives, he said.
The bodies will be autopsied before burial to determine causes of death, he said.
Southeast Asian nations are facing a humanitarian crisis as thousands of migrants from Bangladesh and Myanmar
take to the sea in boats, hoping to settle elsewhere in the region.
In recent weeks, police in Thailand have reported finding graves and camps from human trafficking
on their side of the border, and they have cracked down on people-smuggling there.
That has intensified the crisis at sea. Boats carrying migrants from Myanmar and Bangladesh stay away from the shore, deepening the danger for the people crammed on board.
Many of the migrants are Rohingya Muslims, an ethnic minority fleeing persecution in western Myanmar. There are also economic migrants from Bangladesh seeking work in countries like Malaysia
'We will find more'
Monday's grim announcement came after Malaysia said Sunday that it had discovered mass graves and trafficking camps in a different area near the Thai border.
Malaysian Home Minister Ahmad Zahid Hamidi said those camps were believed to have been in operation for at least five years and were abandoned only when authorities arrived.
He said officials were still counting the number of bodies in the graves, which were found near 17 tents in the Padang Besar area of Perlis state.
"With the cooperation of Thailand, we will find more and more," Zahid told reporters.
The Prime Minister, Najib Razak, vowed late Sunday in a tweet to bring the perpetrators to justice.
"I am deeply concerned with graves found on Malaysian soil purportedly connected to people smuggling. We will find those responsible," he wrote.
Bangladeshi PM: Punish migrants
According to the International Organization for Migration, an estimated 25,000 Southeast Asian migrants took to seas in the first three months of 2015.
In recent weeks, hundreds of migrants have come ashore in Malaysia and in Aceh in Indonesia after making the risky journey south through the Andaman Sea.
Bangladesh's leader, Sheikh Hasina, said Sunday that those seeking to leave the country in illegally should be punished along with the human traffickers who facilitate their escape.
"Side by side with the middlemen, punishment will have to be given to those who are moving from the country in illegal way," Hasina told senior officials Sunday, Bangladesh's state media reported
. "They are tainting the image of the country along with putting their lives in danger."
Authorities are preparing to repatriate 208 Bangladeshi citizens who were rescued by the Myanmar navy in that country's territorial waters, the state-run Global New Light of Myanmar newspaper said
"We have been informed through sources that the rescued Bangladeshis are staying at a refugee center in a madrasa building in the Thandwe area of Rakhine state in Myanmar," the agency quoted Lt. Col Abu Zar, a Bangladeshi border commander, as saying, citing Bangladeshi media.
"Local members of United Nations High Commissioner for Refugees are providing food to the Bangla language people," he said.
The report said dozens of Bangladeshi citizens were stranded in Myanmar territorial waters.
U.S. military request
The Thai military said the U.S. Navy had asked to use one of its airports to help migrants stranded on boats in the Andaman Sea.
The U.S. has asked to keep surveillance aircraft in Phuket after the completion of antisubmarine training exercises, Thai air force spokesman Air Vice Marshal Montol Sanchukorn told CNN. The U.S. and Thai armed forces took part in joint operations, codenamed Guardian Sea, last week, and as a result, U.S. aircraft were permitted to fly in Thai airspace.
Montol said that the U.S. request was made at an operational, rather than formal, level and was misdirected, as permission to use Phuket's international airport would be granted at the discretion of Thailand's airport authority.
He said he told U.S. military liaisons to make their request through governmental channels.
At a meeting last week, Indonesia and Malaysia agreed to accept thousands of migrants temporarily as long as the international community helps resettle them within one year.
Thailand has yet to announce what role it will play, although in a joint statement, the three nations said they had all taken measures beyond their international obligations to address the "current influx of irregular migrants."