The guard said that three passengers were injured.
Authorities said earlier that some people had jumped into the water in panic before dawn as the vessel began to tilt to the right.
The ship sank about six nautical miles off the west coast of Zamboanga peninsula on Mindanao island, Teodoro said.
Al Jazeera's Marga Ortigas, reporting from Manila, said quoting the coast guard that a little more than 80 people were still unaccounted for.
"They don't want to qualify these people as missing or indeed possible fatalities ... because they could have also been taken to shore by fishing vessels that may not have had radio contact with the rescuers," she said.
"No names have been released, and indeed no names even of the fatalities at the moment."
|The ferry was scheduled to arrive in Iloilo in the central Philippines on Sunday [AFP]
Navy ships were deployed and air force helicopters were helping in the rescue.
The ship left the southern city of General Santos on Saturday and was scheduled to arrive in Iloilo city in the central Philippines on Sunday.
The ferry apparently ran into some problems midway and began to list, according to Jess Supan, vice-president of the Aboitiz Transport System, the ferry owner.
Commodore Rudy Isorena, a regional coastguard chief, said the cause of the accident was not yet clear and the weather in the area had not been too bad.
"We cannot say yet as to the cause as the attention right now is being given to the search and rescue of passengers," he said.
The weather was generally fair in the Zamboanga peninsula region, about 860km south of Manila, although a tropical storm was reported in the country's mountainous north, the coast guard said.
Sea accidents are common in the Philippine archipelago because of tropical storms, badly maintained boats and weak enforcement of safety regulations.
Our correspondent said authorities consider the incident a "close call" a year after another fatal ferry accident.
"They are saying they did avert what could have been yet another maritime disaster," Ortigas said.
"It's just been a year since the Princess of the Stars sank during a typhoon in June of last year and most of the passengers, some 500 people, were all dead on that one.
"So they consider this a rather close call but they are very pleased that some 800 people have indeed survived."